With all of the "colorful" language I see sometimes, I thought it would be fun to try it myself. It's fun but annoying at the same time
How about a "/setprefix <text>" command line ability so you can hotkey the prefix to the chat window with the focus.
Like
/setprefix /g <!--color r=0.7 g=0.5 b=0.1>
Then you can have the colors and groups you want to chat to in what color just by clicking.
Unless there is a better way to switch your prefix text