stay clear or the green, red and blue.
Green I can understand. Self-explanatory.
Red has been used quite frequently for emphasis in ordinary posts, as well as by moderators when issuing a warning or banning, accompanied by a colored dot. It's pretty simple to distinguish these two uses, the former which has occurred without a shred of complaint from the powers that be. Until now.
Blue? Thomas uses it in his welcome to converts, and it's been used countless times for block quotes and for people's usernames within an otherwise black-letter post, again, without a shred of complaint from the powers that be. Until now.