[Xenon]

hmm, there is a way you can try: create a new profilefield editable by the user, let's say font specifics (50 chars i think is enough.)

then just edit your postbit template
find $post[username] and change it into <font $post[fieldX]>$post[username]</font>

Replace the X with the new fieldid, and when they fill their fiel with for example color="red" it should change the username into red.