Originally Posted by After Shock Media

Blue - admin or works with ICS/Adult.com/Playboy.
Red - 50k posts or more.
Green - 10k posts or more.
Orange - 0-9,999 posts and default.
White - you clicked the name.

Color changes are not automatic and must be done by a mod. So you may see a few who have more than 10k without being green etc.