Sure, it probably doesn't help out someone's writing skills, but unless you are relying on it to show who is speaking, I don't see how it can hurt.  Books and roleplayers are different media in the sense that one is printed (or usually printed) while roleplays (at least play-by-post ones) are electronic.  Color ink by nature is more expensive to use than pure black ink.  Here, we don't have to worry about that.  I don't mind it if it is not being used as a crutch.