Hi,

please see this quick fix on completion prefix highlighting.
it's based on commit e59452c.

(thanks pointing out the development branch. an extension seems to be really better here because older versions discard the whole LS_COLORS if find an unsupported indicator)

Date:   Tue Dec 7 23:54:15 2021 +0100

    bugfix

diff --git a/lib/readline/colors.c b/lib/readline/colors.c
index 18b640e..050142f 100644
--- a/lib/readline/colors.c
+++ b/lib/readline/colors.c
@@ -108,7 +108,7 @@ _rl_custom_readline_prefix (void)

   len = strlen (RL_COLOR_PREFIX_EXTENSION);
   for (ext = _rl_color_ext_list; ext; ext = ext->next)
-    if (ext->ext.len == len && STREQ (ext->ext.string, RL_COLOR_PREFIX_EXTENSION))
+    if (ext->ext.len == len && STREQN (ext->ext.string, RL_COLOR_PREFIX_EXTENSION, ext->ext.len))
       return (&ext->seq);
   return (NULL);
 }