diff --git a/CHANGELOG.md b/CHANGELOG.md
index f6b715488..99b28be03 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ SPDX-License-Identifier: GPL-3.0-or-later
 
 ### Added
 
+- core: add `themable` flag on configuration options
 - relay/api: add resource `GET /api/scripts`
 - relay: add option relay.network.unix_socket_permissions ([#2317](https://github.com/weechat/weechat/issues/2317))
 - script: add info "script_languages"
diff --git a/doc/en/weechat_plugin_api.en.adoc b/doc/en/weechat_plugin_api.en.adoc
index c84e790e7..981882f0e 100644
--- a/doc/en/weechat_plugin_api.en.adoc
+++ b/doc/en/weechat_plugin_api.en.adoc
@@ -7367,7 +7367,7 @@ section = weechat.config_search_section(config_file, "section")
 
 ==== config_new_option
 
-_Updated in 1.5, 4.1.0._
+_Updated in 1.5, 4.1.0, 4.10.0._
 
 Create a new option in a section of a configuration file.
 
@@ -7413,7 +7413,9 @@ Arguments:
   option name (the value of parent option will be displayed in `/set` command
   output if this option is "null"), the syntax is then:
   "name << file.section.option"
-* _type_: type of option:
+* _type_: type of option; any type can be suffixed with `+|themable+` to mark
+  the option as themable, so that it can be set by the `/theme` command
+  (options of type _color_ are always themable) _(WeeChat ≥ 4.10.0)_:
 ** _boolean_: boolean value (on/off)
 ** _integer_: integer value
 ** _string_: string value
@@ -7499,7 +7501,7 @@ struct t_config_option *option_int =
 
 /* string */
 struct t_config_option *option_str =
-    weechat_config_new_option (config_file, section, "option_str", "string",
+    weechat_config_new_option (config_file, section, "option_str", "string|themable",
                                "My option, type string",
                                NULL,
                                0, 0,
@@ -7575,7 +7577,7 @@ option_int = weechat.config_new_option(config_file, section, "option_int", "inte
     "", "",
     "", "")
 
-option_str = weechat.config_new_option(config_file, section, "option_str", "string",
+option_str = weechat.config_new_option(config_file, section, "option_str", "string|themable",
     "My option, type string",
     "", 0, 0, "test", "test", 1,
     "option_str_check_value_cb", "",
diff --git a/doc/fr/weechat_plugin_api.fr.adoc b/doc/fr/weechat_plugin_api.fr.adoc
index a6c2c36dd..1cf6085dc 100644
--- a/doc/fr/weechat_plugin_api.fr.adoc
+++ b/doc/fr/weechat_plugin_api.fr.adoc
@@ -7488,7 +7488,7 @@ section = weechat.config_search_section(config_file, "section")
 
 ==== config_new_option
 
-_Mis à jour dans la 1.5, 4.1.0._
+_Mis à jour dans la 1.5, 4.1.0, 4.10.0._
 
 Créer une nouvelle option dans une section d'un fichier de configuration.
 
@@ -7534,7 +7534,10 @@ Paramètres :
   d'une option parente (la valeur de l'option parente sera affichée dans la
   sortie de `/set` si cette option est "null"), la syntaxe est alors :
   "name << file.section.option"
-* _type_ : type de l'option :
+* _type_ : type de l'option ; n'importe quel type peut être suffixé par
+  `+|themable+` pour rendre l'option modifiable par un thème, afin qu'elle
+  puisse être définie par la commande `/theme` (les options de type _color_
+  sont toujours modifiables par un thème) _(WeeChat ≥ 4.10.0)_ :
 ** _boolean_ : valeur booléenne (on/off)
 ** _integer_ : valeur entière
 ** _string_ : une chaîne de caractères
@@ -7625,7 +7628,7 @@ struct t_config_option *option_int =
 
 /* chaîne */
 struct t_config_option *option_str =
-    weechat_config_new_option (config_file, section, "option_str", "string",
+    weechat_config_new_option (config_file, section, "option_str", "string|themable",
                                "Mon option, type chaîne",
                                NULL,
                                0, 0,
@@ -7701,7 +7704,7 @@ option_int = weechat.config_new_option(config_file, section, "option_int", "inte
     "", "",
     "", "")
 
-option_str = weechat.config_new_option(config_file, section, "option_str", "string",
+option_str = weechat.config_new_option(config_file, section, "option_str", "string|themable",
     "Mon option, type chaîne",
     "", 0, 0, "test", "test", 1,
     "option_str_check_value_cb", "",
diff --git a/doc/it/weechat_plugin_api.it.adoc b/doc/it/weechat_plugin_api.it.adoc
index 6e9e222cb..6482d611c 100644
--- a/doc/it/weechat_plugin_api.it.adoc
+++ b/doc/it/weechat_plugin_api.it.adoc
@@ -7661,7 +7661,7 @@ section = weechat.config_search_section(config_file, "section")
 ==== config_new_option
 
 // TRANSLATION MISSING
-_Updated in 1.5, 4.1.0._
+_Updated in 1.5, 4.1.0, 4.10.0._
 
 Crea una nuova opzione nella sezione di un file di configurazione.
 
@@ -7708,7 +7708,10 @@ Argomenti:
   option name (the value of parent option will be displayed in `/set` command
   output if this option is "null"), the syntax is then:
   "name << file.section.option"
-* _type_: tipo dell'opzione:
+// TRANSLATION MISSING
+* _type_: type of option; any type can be suffixed with `+|themable+` to mark
+  the option as themable, so that it can be set by the `/theme` command
+  (options of type _color_ are always themable) _(WeeChat ≥ 4.10.0)_:
 ** _boolean_: valore booleano (on/off)
 ** _integer_: valore intero
 ** _string_: valore stringa
@@ -7799,7 +7802,7 @@ struct t_config_option *option_int =
 
 /* stringa */
 struct t_config_option *option_str =
-    weechat_config_new_option (config_file, section, "option_str", "string",
+    weechat_config_new_option (config_file, section, "option_str", "string|themable",
                                "My option, type string",
                                NULL,
                                0, 0,
@@ -7875,7 +7878,7 @@ option_int = weechat.config_new_option(config_file, section, "option_int", "inte
     "", "",
     "", "")
 
-option_str = weechat.config_new_option(config_file, section, "option_str", "string",
+option_str = weechat.config_new_option(config_file, section, "option_str", "string|themable",
     "My option, type string",
     "", 0, 0, "test", "test", 1,
     "option_str_check_value_cb", "",
diff --git a/doc/ja/weechat_plugin_api.ja.adoc b/doc/ja/weechat_plugin_api.ja.adoc
index 171f5cf02..b3c9df0fc 100644
--- a/doc/ja/weechat_plugin_api.ja.adoc
+++ b/doc/ja/weechat_plugin_api.ja.adoc
@@ -7472,7 +7472,7 @@ section = weechat.config_search_section(config_file, "section")
 ==== config_new_option
 
 // TRANSLATION MISSING
-_Updated in 1.5, 4.1.0._
+_Updated in 1.5, 4.1.0, 4.10.0._
 
 設定ファイルのあるセクションに新しいオプションを作成。
 
@@ -7518,7 +7518,10 @@ struct t_config_option *weechat_config_new_option (
   (このオプションが "null" の場合、親オプションの値が `/set`
   コマンドの出力に表示されます)。以下の構文を使ってください:
   "name << file.section.option"
-* _type_: オプションの型:
+// TRANSLATION MISSING
+* _type_: type of option; any type can be suffixed with `+|themable+` to mark
+  the option as themable, so that it can be set by the `/theme` command
+  (options of type _color_ are always themable) _(WeeChat ≥ 4.10.0)_:
 ** _boolean_: ブール値 (on/off)
 ** _integer_: 整数値
 ** _string_: 文字列
@@ -7606,7 +7609,7 @@ struct t_config_option *option_int =
 
 /* string */
 struct t_config_option *option_str =
-    weechat_config_new_option (config_file, section, "option_str", "string",
+    weechat_config_new_option (config_file, section, "option_str", "string|themable",
                                "My option, type string",
                                NULL,
                                0, 0,
@@ -7682,7 +7685,7 @@ option_int = weechat.config_new_option(config_file, section, "option_int", "inte
     "", "",
     "", "")
 
-option_str = weechat.config_new_option(config_file, section, "option_str", "string",
+option_str = weechat.config_new_option(config_file, section, "option_str", "string|themable",
     "My option, type string",
     "", 0, 0, "test", "test", 1,
     "option_str_check_value_cb", "",
diff --git a/doc/sr/weechat_plugin_api.sr.adoc b/doc/sr/weechat_plugin_api.sr.adoc
index a37cc32ac..55ee60c6b 100644
--- a/doc/sr/weechat_plugin_api.sr.adoc
+++ b/doc/sr/weechat_plugin_api.sr.adoc
@@ -7171,7 +7171,7 @@ section = weechat.config_search_section(config_file, "section")
 
 ==== config_new_option
 
-_Ажурирано у верзији 1.5, 4.1.0._
+_Ажурирано у верзији 1.5, 4.1.0, 4.10.0._
 
 Креира нову опцију у одељку конфигурационог фајла.
 
@@ -7214,7 +7214,10 @@ struct t_config_option *weechat_config_new_option (
 * _config_file_: показивач на конфигурациони фајл
 * _section_: показивач на одељак
 * _name_: име опције; у програм у WeeChat верзије ≥ 1.4, име може да укључи и име родитељске опције (у случају да је ова опција „null”, вредност родитељске опције ће се приказати у излазу команде `/set`), тада је синтакса: „име << фајл.одељак.опција”
-* _type_: тип опције:
+// TRANSLATION MISSING
+* _type_: type of option; any type can be suffixed with `+|themable+` to mark
+  the option as themable, so that it can be set by the `/theme` command
+  (options of type _color_ are always themable) _(WeeChat ≥ 4.10.0)_:
 ** _boolean_: логичка вредност (on/off)
 ** _integer_: целобројна вредност
 ** _string_: стринг вредност
@@ -7287,7 +7290,7 @@ struct t_config_option *option_int =
 
 /* стринг */
 struct t_config_option *option_str =
-    weechat_config_new_option (config_file, section, "option_str", "string",
+    weechat_config_new_option (config_file, section, "option_str", "string|themable",
                                "My option, type string",
                                NULL,
                                0, 0,
@@ -7363,7 +7366,7 @@ option_int = weechat.config_new_option(config_file, section, "option_int", "inte
     "", "",
     "", "")
 
-option_str = weechat.config_new_option(config_file, section, "option_str", "string",
+option_str = weechat.config_new_option(config_file, section, "option_str", "string|themable",
     "My option, type string",
     "", 0, 0, "test", "test", 1,
     "option_str_check_value_cb", "",
diff --git a/src/core/core-config-file.c b/src/core/core-config-file.c
index 9d2def76d..b408aa925 100644
--- a/src/core/core-config-file.c
+++ b/src/core/core-config-file.c
@@ -648,6 +648,7 @@ config_file_option_malloc (void)
         new_option->name = NULL;
         new_option->parent_name = NULL;
         new_option->type = 0;
+        new_option->themable = 0;
         new_option->description = NULL;
         new_option->string_values = NULL;
         new_option->min = 0;
@@ -704,17 +705,37 @@ config_file_new_option (struct t_config_file *config_file,
                         void *callback_delete_data)
 {
     struct t_config_option *new_option;
-    int var_type, int_value, argc, i, index_value, number;
-    const char *pos;
-    char *option_name, *parent_name;
+    int var_type, int_value, argc, i, index_value, number, themable;
+    const char *pos, *ptr_type;
+    char *option_name, *parent_name, *type_name;
 
     new_option = NULL;
     option_name = NULL;
     parent_name = NULL;
+    type_name = NULL;
+    themable = 0;
 
     if (!name || !type)
         goto error;
 
+    /*
+     * extract optional "|themable" suffix from type
+     * (e.g.: "string|themable" for a string option that contains color names)
+     */
+    pos = strchr (type, '|');
+    if (pos && (strcmp (pos, "|themable") == 0))
+    {
+        type_name = string_strndup (type, pos - type);
+        if (!type_name)
+            goto error;
+        ptr_type = type_name;
+        themable = 1;
+    }
+    else
+    {
+        ptr_type = type;
+    }
+
     pos = strstr (name, " << ");
     if (pos)
     {
@@ -735,7 +756,7 @@ config_file_new_option (struct t_config_file *config_file,
     var_type = -1;
     for (i = 0; i < CONFIG_NUM_OPTION_TYPES; i++)
     {
-        if (strcmp (type, config_option_type_string[i]) == 0)
+        if (strcmp (ptr_type, config_option_type_string[i]) == 0)
         {
             var_type = i;
             break;
@@ -745,10 +766,14 @@ config_file_new_option (struct t_config_file *config_file,
     {
         gui_chat_printf (NULL, "%sUnknown option type \"%s\"",
                          gui_chat_prefix[GUI_CHAT_PREFIX_ERROR],
-                         type);
+                         ptr_type);
         goto error;
     }
 
+    /* color options are always themable */
+    if (var_type == CONFIG_OPTION_TYPE_COLOR)
+        themable = 1;
+
     /*
      * compatibility with versions < 4.1.0: force enum type for an integer
      * with string values
@@ -785,6 +810,7 @@ config_file_new_option (struct t_config_file *config_file,
             goto error;
         new_option->parent_name = (parent_name) ? strdup (parent_name) : NULL;
         new_option->type = var_type;
+        new_option->themable = themable;
         if (description)
         {
             new_option->description = strdup (description);
@@ -970,6 +996,7 @@ error:
 end:
     free (option_name);
     free (parent_name);
+    free (type_name);
     return new_option;
 }
 
@@ -2440,6 +2467,8 @@ config_file_option_get_pointer (struct t_config_option *option,
         return option->parent_name;
     else if (strcmp (property, "type") == 0)
         return &option->type;
+    else if (strcmp (property, "themable") == 0)
+        return &option->themable;
     else if (strcmp (property, "description") == 0)
         return option->description;
     else if (strcmp (property, "string_values") == 0)
@@ -4249,6 +4278,7 @@ config_file_hdata_config_option_cb (const void *pointer, void *data,
         HDATA_VAR(struct t_config_option, name, STRING, 0, NULL, NULL);
         HDATA_VAR(struct t_config_option, parent_name, STRING, 0, NULL, NULL);
         HDATA_VAR(struct t_config_option, type, INTEGER, 0, NULL, NULL);
+        HDATA_VAR(struct t_config_option, themable, INTEGER, 0, NULL, NULL);
         HDATA_VAR(struct t_config_option, description, STRING, 0, NULL, NULL);
         HDATA_VAR(struct t_config_option, string_values, STRING, 0, "*,*", NULL);
         HDATA_VAR(struct t_config_option, min, INTEGER, 0, NULL, NULL);
@@ -4361,6 +4391,8 @@ config_file_add_option_to_infolist (struct t_infolist *infolist,
     {
         goto error;
     }
+    if (!infolist_new_var_integer (ptr_item, "themable", option->themable))
+        goto error;
     if (option->value)
     {
         value = config_file_option_value_to_string (option, 0, 0, 0);
@@ -4525,6 +4557,7 @@ config_file_print_log (void)
                 log_printf ("        name . . . . . . . . . . . . : '%s'", ptr_option->name);
                 log_printf ("        parent_name. . . . . . . . . : '%s'", ptr_option->parent_name);
                 log_printf ("        type . . . . . . . . . . . . : %d", ptr_option->type);
+                log_printf ("        themable . . . . . . . . . . : %d", ptr_option->themable);
                 log_printf ("        description. . . . . . . . . : '%s'", ptr_option->description);
                 log_printf ("        string_values. . . . . . . . : %p", ptr_option->string_values);
                 log_printf ("        min. . . . . . . . . . . . . : %d", ptr_option->min);
diff --git a/src/core/core-config-file.h b/src/core/core-config-file.h
index 1298f0c50..f067e2b3a 100644
--- a/src/core/core-config-file.h
+++ b/src/core/core-config-file.h
@@ -154,6 +154,8 @@ struct t_config_option
     char *parent_name;                     /* parent name (to inherit the   */
                                            /* value from another option)    */
     enum t_config_option_type type;        /* type                          */
+    int themable;                          /* 1 if option is themable       */
+                                           /* (color, or string with color) */
     char *description;                     /* description                   */
     char **string_values;                  /* allowed string values         */
     int min, max;                          /* min and max for value         */
diff --git a/src/core/core-config.c b/src/core/core-config.c
index 3cb1ae0c9..aedcbbb0f 100644
--- a/src/core/core-config.c
+++ b/src/core/core-config.c
@@ -3450,7 +3450,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
         config_look_buffer_time_format = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "buffer_time_format", "string",
+            "buffer_time_format", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("time format for each line displayed in buffers (see man "
                "strftime for date/time specifiers, extra specifiers are "
@@ -3474,7 +3474,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_buffer_time_same = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "buffer_time_same", "string",
+            "buffer_time_same", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("time displayed for a message with same time as previous message: "
                "use a space \" \" to hide time, another string to display this "
@@ -3641,7 +3641,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_day_change_message_1date = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "day_change_message_1date", "string",
+            "day_change_message_1date", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("message displayed when the day has changed, with one date "
                "displayed (for example at beginning of buffer) (see man "
@@ -3654,7 +3654,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_day_change_message_2dates = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "day_change_message_2dates", "string",
+            "day_change_message_2dates", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("message displayed when the day has changed, with two dates "
                "displayed (between two messages); the second date specifiers "
@@ -3971,7 +3971,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_item_time_format = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "item_time_format", "string",
+            "item_time_format", "string|themable",
             N_("time format for \"time\" bar item (see man strftime for "
                "date/time specifiers) (note: content is evaluated, so you can "
                "use colors with format \"${color:xxx}\", see /help eval)"),
@@ -4026,7 +4026,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_nick_color_force = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "nick_color_force", "string",
+            "nick_color_force", "string|themable",
             N_("force color for some nicks: hash computed with nickname "
                "to find color will not be used for these nicks (format is: "
                "\"nick1:color1;nick2:color2\"); look up for nicks is with "
@@ -4118,7 +4118,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
         config_look_prefix[GUI_CHAT_PREFIX_ERROR] = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "prefix_error", "string",
+            "prefix_error", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("prefix for error messages (note: content is evaluated, so you "
                "can use colors with format \"${color:xxx}\", see /help eval)"),
@@ -4128,7 +4128,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_prefix[GUI_CHAT_PREFIX_NETWORK] = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "prefix_network", "string",
+            "prefix_network", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("prefix for network messages (note: content is evaluated, so you "
                "can use colors with format \"${color:xxx}\", see /help eval)"),
@@ -4138,7 +4138,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_prefix[GUI_CHAT_PREFIX_ACTION] = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "prefix_action", "string",
+            "prefix_action", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("prefix for action messages (note: content is evaluated, so you "
                "can use colors with format \"${color:xxx}\", see /help eval)"),
@@ -4148,7 +4148,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_prefix[GUI_CHAT_PREFIX_JOIN] = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "prefix_join", "string",
+            "prefix_join", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("prefix for join messages (note: content is evaluated, so you "
                "can use colors with format \"${color:xxx}\", see /help eval)"),
@@ -4158,7 +4158,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_look_prefix[GUI_CHAT_PREFIX_QUIT] = config_file_new_option (
             weechat_config_file, weechat_config_section_look,
-            "prefix_quit", "string",
+            "prefix_quit", "string|themable",
             /* TRANSLATORS: string "${color:xxx}" must NOT be translated */
             N_("prefix for quit messages (note: content is evaluated, so you "
                "can use colors with format \"${color:xxx}\", see /help eval)"),
@@ -4647,7 +4647,7 @@ config_weechat_init_options (void)
             NULL, NULL, NULL);
         config_color_chat_nick_colors = config_file_new_option (
             weechat_config_file, weechat_config_section_color,
-            "chat_nick_colors", "string",
+            "chat_nick_colors", "string|themable",
             /* TRANSLATORS: please do not translate "lightred:blue" */
             N_("text color for nicks (comma separated list of colors, "
                "background is allowed with format: \"fg:bg\", for example: "
@@ -4918,7 +4918,7 @@ config_weechat_init_options (void)
         /* eval syntax highlighting colors (for "${raw_hl:xxx}" and "${hl:xxx}") */
         config_color_eval_syntax_colors = config_file_new_option (
             weechat_config_file, weechat_config_section_color,
-            "eval_syntax_colors", "string",
+            "eval_syntax_colors", "string|themable",
             /* TRANSLATORS: please do not translate "lightred:blue" */
             N_("text color for syntax highlighting in evaluated strings, "
                "with \"${raw_hl:...}\" and \"${hl:...}\" (comma separated "
diff --git a/src/plugins/buflist/buflist-config.c b/src/plugins/buflist/buflist-config.c
index 942c67815..2b21ad84e 100644
--- a/src/plugins/buflist/buflist-config.c
+++ b/src/plugins/buflist/buflist-config.c
@@ -645,7 +645,7 @@ buflist_config_init (void)
     {
         buflist_config_format_buffer = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "buffer", "string",
+            "buffer", "string|themable",
             N_("format of each line with a buffer "
                "(note: content is evaluated, see /help buflist); "
                "example: standard format for bar item \"buflist\" and only the "
@@ -663,7 +663,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_buffer_current = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "buffer_current", "string",
+            "buffer_current", "string|themable",
             N_("format for the line with current buffer "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color:,17}${format_buffer}", NULL, 0,
@@ -672,7 +672,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_hotlist = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "hotlist", "string",
+            "hotlist", "string|themable",
             N_("format for hotlist "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0,
@@ -683,7 +683,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_hotlist_level[3] = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "hotlist_highlight", "string",
+            "hotlist_highlight", "string|themable",
             N_("format for a buffer with hotlist level \"highlight\" "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color:magenta}", NULL, 0,
@@ -692,7 +692,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_hotlist_level[0] = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "hotlist_low", "string",
+            "hotlist_low", "string|themable",
             N_("format for a buffer with hotlist level \"low\" "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color:white}", NULL, 0,
@@ -701,7 +701,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_hotlist_level[1] = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "hotlist_message", "string",
+            "hotlist_message", "string|themable",
             N_("format for a buffer with hotlist level \"message\" "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color:brown}", NULL, 0,
@@ -710,7 +710,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_hotlist_level_none = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "hotlist_none", "string",
+            "hotlist_none", "string|themable",
             N_("format for a buffer not in hotlist "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color:default}", NULL, 0,
@@ -719,7 +719,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_hotlist_level[2] = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "hotlist_private", "string",
+            "hotlist_private", "string|themable",
             N_("format for a buffer with hotlist level \"private\" "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color:green}", NULL, 0,
@@ -728,7 +728,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_hotlist_separator = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "hotlist_separator", "string",
+            "hotlist_separator", "string|themable",
             N_("separator for counts in hotlist "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color:default},", NULL, 0,
@@ -737,7 +737,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_indent = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "indent", "string",
+            "indent", "string|themable",
             N_("string displayed to indent channel, private and list buffers "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "  ", NULL, 0,
@@ -746,7 +746,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_lag = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "lag", "string",
+            "lag", "string|themable",
             N_("format for lag on an IRC server buffer "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0,
@@ -757,7 +757,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_name = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "name", "string",
+            "name", "string|themable",
             N_("format for buffer name "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${name}", NULL, 0,
@@ -766,7 +766,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_nick_prefix = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "nick_prefix", "string",
+            "nick_prefix", "string|themable",
             N_("format for nick prefix on a channel "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0, "${color_nick_prefix}${nick_prefix}", NULL, 0,
@@ -775,7 +775,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_number = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "number", "string",
+            "number", "string|themable",
             N_("format for buffer number, ${number} is the indented number "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0,
@@ -786,7 +786,7 @@ buflist_config_init (void)
             NULL, NULL, NULL);
         buflist_config_format_tls_version = weechat_config_new_option (
             buflist_config_file, buflist_config_section_format,
-            "tls_version", "string",
+            "tls_version", "string|themable",
             N_("format for TLS version on an IRC server buffer "
                "(note: content is evaluated, see /help buflist)"),
             NULL, 0, 0,
diff --git a/src/plugins/fset/fset-config.c b/src/plugins/fset/fset-config.c
index fd3742f9e..ac075b676 100644
--- a/src/plugins/fset/fset-config.c
+++ b/src/plugins/fset/fset-config.c
@@ -572,7 +572,7 @@ fset_config_init (void)
             NULL, NULL, NULL);
         fset_config_format_option[1] = weechat_config_new_option (
             fset_config_file, fset_config_section_format,
-            "option2", "string",
+            "option2", "string|themable",
             N_("second format of each line, used when option "
                "fset.look.format_number is set to 2 "
                "(note: content is evaluated, see /help fset); "
diff --git a/src/plugins/irc/irc-config.c b/src/plugins/irc/irc-config.c
index 004c8cfd1..5b4ef16d6 100644
--- a/src/plugins/irc/irc-config.c
+++ b/src/plugins/irc/irc-config.c
@@ -3957,7 +3957,7 @@ irc_config_init (void)
             NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
         irc_config_color_mirc_remap = weechat_config_new_option (
             irc_config_file, irc_config_section_color,
-            "mirc_remap", "string",
+            "mirc_remap", "string|themable",
             /* TRANSLATORS: please do not translate the list of WeeChat color names at the end of string */
             N_("remap mirc colors in messages using a hashtable (used only "
                "for standard colors, not RGB colors): keys are \"fg,bg\" as "
@@ -3975,7 +3975,7 @@ irc_config_init (void)
             NULL, NULL, NULL);
         irc_config_color_nick_prefixes = weechat_config_new_option (
             irc_config_file, irc_config_section_color,
-            "nick_prefixes", "string",
+            "nick_prefixes", "string|themable",
             N_("color for nick prefixes using mode char (o=op, h=halfop, "
                "v=voice, ..), format is: \"o:color1;h:color2;v:color3\" (if a "
                "mode is not found, WeeChat will try with next modes received "
@@ -4006,7 +4006,7 @@ irc_config_init (void)
             NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
         irc_config_color_term_remap = weechat_config_new_option (
             irc_config_file, irc_config_section_color,
-            "term_remap", "string",
+            "term_remap", "string|themable",
             N_("remap terminal color numbers in messages using a hashtable "
                "(used only for RGB colors as hexadecimal, which are first "
                "translated to terminal color numbers): keys are \"fg,bg\" as "
diff --git a/src/plugins/python/weechat.pyi b/src/plugins/python/weechat.pyi
index a9f5abb82..3fdc603a0 100644
--- a/src/plugins/python/weechat.pyi
+++ b/src/plugins/python/weechat.pyi
@@ -635,7 +635,7 @@ def config_new_option(config_file: str, section: str, name: str, type: str, desc
             "", "",
             "", "")
 
-        option_str = weechat.config_new_option(config_file, section, "option_str", "string",
+        option_str = weechat.config_new_option(config_file, section, "option_str", "string|themable",
             "My option, type string",
             "", 0, 0, "test", "test", 1,
             "option_str_check_value_cb", "",
diff --git a/src/plugins/relay/relay-config.c b/src/plugins/relay/relay-config.c
index 989a16e59..da4aebd64 100644
--- a/src/plugins/relay/relay-config.c
+++ b/src/plugins/relay/relay-config.c
@@ -1934,7 +1934,7 @@ relay_config_init (void)
             NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
         relay_config_api_remote_input_cmd_local = weechat_config_new_option (
             relay_config_file, relay_config_section_api,
-            "remote_input_cmd_local", "string",
+            "remote_input_cmd_local", "string|themable",
             N_("text displayed after user input when the command would be "
                "executed locally (NOT sent to the remote WeeChat) "
                "(note: content is evaluated, see /help eval)"),
@@ -1942,7 +1942,7 @@ relay_config_init (void)
             NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
         relay_config_api_remote_input_cmd_remote = weechat_config_new_option (
             relay_config_file, relay_config_section_api,
-            "remote_input_cmd_remote", "string",
+            "remote_input_cmd_remote", "string|themable",
             N_("text displayed after user input when the command would be "
                "executed on the remote WeeChat (NOT executed locally) "
                "(note: content is evaluated, see /help eval)"),
diff --git a/tests/unit/core/test-core-config-file.cpp b/tests/unit/core/test-core-config-file.cpp
index 2a24863f4..6c0bb3274 100644
--- a/tests/unit/core/test-core-config-file.cpp
+++ b/tests/unit/core/test-core-config-file.cpp
@@ -394,6 +394,36 @@ TEST(CoreConfigFile, OptionMalloc)
     /* TODO: write tests */
 }
 
+/*
+ * Create an option with the given type, read its "themable" flag, then free
+ * it.
+ *
+ * Return the value of the "themable" flag (0 or 1), or -1 if the option could
+ * not be created (invalid type).
+ */
+
+int
+test_new_option_themable (struct t_config_section *section,
+                          const char *name, const char *type,
+                          const char *string_values,
+                          const char *default_value)
+{
+    struct t_config_option *option;
+    int themable;
+
+    option = config_file_new_option (
+        weechat_config_file, section,
+        name, type, "", string_values, 0, 123456, default_value, NULL, 0,
+        NULL, NULL, NULL,
+        NULL, NULL, NULL,
+        NULL, NULL, NULL);
+    if (!option)
+        return -1;
+    themable = option->themable;
+    config_file_option_free (option, 0);
+    return themable;
+}
+
 /*
  * Test functions:
  *   config_file_new_option
@@ -401,7 +431,70 @@ TEST(CoreConfigFile, OptionMalloc)
 
 TEST(CoreConfigFile, NewOption)
 {
-    /* TODO: write tests */
+    struct t_config_option *ptr_option;
+    int *ptr_themable;
+
+    /* plain types are not themable */
+    LONGS_EQUAL(0, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "boolean", NULL, "off"));
+    LONGS_EQUAL(0, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "integer", NULL, "100"));
+    LONGS_EQUAL(0, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "string", NULL, "value"));
+    LONGS_EQUAL(0, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "enum", "v1|v2|v3", "v2"));
+
+    /* color options are always themable, even without the suffix */
+    LONGS_EQUAL(1, test_new_option_themable (
+                    weechat_config_section_color,
+                    "test_themable", "color", NULL, "blue"));
+
+    /* the "|themable" suffix marks an option of any type as themable */
+    LONGS_EQUAL(1, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "boolean|themable", NULL, "off"));
+    LONGS_EQUAL(1, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "integer|themable", NULL, "100"));
+    LONGS_EQUAL(1, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "string|themable", NULL, "value"));
+    LONGS_EQUAL(1, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "enum|themable", "v1|v2|v3", "v2"));
+    LONGS_EQUAL(1, test_new_option_themable (
+                    weechat_config_section_color,
+                    "test_themable", "color|themable", NULL, "blue"));
+
+    /* an invalid type or unknown suffix is refused (option not created) */
+    LONGS_EQUAL(-1, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "string|xxx", NULL, "value"));
+    LONGS_EQUAL(-1, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "string|", NULL, "value"));
+    LONGS_EQUAL(-1, test_new_option_themable (
+                    weechat_config_section_look,
+                    "test_themable", "xxx", NULL, "value"));
+
+    /* the flag is reachable via config_file_option_get_pointer */
+    ptr_option = config_file_new_option (
+        weechat_config_file, weechat_config_section_look,
+        "test_themable", "string|themable", "", NULL, 0, 0, "value", NULL, 0,
+        NULL, NULL, NULL,
+        NULL, NULL, NULL,
+        NULL, NULL, NULL);
+    CHECK(ptr_option);
+    ptr_themable = (int *)config_file_option_get_pointer (ptr_option,
+                                                          "themable");
+    CHECK(ptr_themable);
+    POINTERS_EQUAL(&ptr_option->themable, ptr_themable);
+    LONGS_EQUAL(1, *ptr_themable);
+    config_file_option_free (ptr_option, 0);
 }
 
 /*