Well let me tell ya, as fun as it is for you to send colored
text, it's twice as annoying to others. It's best to let others
decide what color your text should be on their end because more
often than not, your colored text will clash with their background
and that you can't change. But if you insist...

Code:
on *:INPUT:#: {
  var %comchar = / $readini($mircini,text,commandchar),%color = 04
  if (($istok(%comchar,$left($1,1),32)) && (!$ctrlenter)) return
  !msg # $+(,%color,$1-)
  haltdef
}


Set %color to whatever color you want your text to be.
Paste that code into your script editor (Alt+R).