As far as I can tell, the colors in mirc are updated apon joins, parts, etc. When the user list is updated, mirc uses the default color scheme. The only think I would recommend is making a timer, or indeed going with on text and on join events to 'refresh' the nicklist as it changes. If you join a channel, then the script (or I assume you are doing some sort of a /cline) wille xecute. When a user joines after you, is mode changed, or parts the nicklist itself is colors according to your mIRC preferences..
Maybe I am wrong in assuming that you did infact use another method then /cline, but as far as I can see try making a timer, or on mode/join/part event triggers.
