I don't know if it has been mentioned before, but I think mIRC used to consider color codes 16-98 to simply be repeats of 0-15. Now, it seems to consider 16-98 to be default text color. If other clients do the same thing (accept color codes 16-98 without errors) then mIRC could actually send extended color codes to channels. The non-mIRC clients would simply see the colors as however their client is set to render them. Other mIRC clients would see the correct colors, of course.