Formatting, when used in a discrete manner, adds a lot to a story. Different colored fonts in the main text is not acceptable, IMO.

A bit of bold here and there for scene shifts or chapter titles, as Craker said, italics or caps for emphasis in the text, and indentation (which ezboard doesn't support. :( ) for new paragraphs is the best.

edit: that being said, almost anything in moderation can add to writing. Colors may be acceptable in a few places. I just can't think of any.