What do the halos mean around people's profile pictures?
Blue - Fitocracy Heroes. They're premium users that get extra benefits like private messaging, Duels, and a weekly insights report. What is Hero?
Orange - Team Fitness Coaches. They run Fitocracy's online training programs. You can see them by tapping on 'Hire a Trainer' in the top left navigation (aka the 'burger' menu).
Purple - Fitocracy Staff. These folks work at Fitocracy. They're usually quite helpful and (mostly) harmless, unless you poke them with a stick, feed them after midnight, or steal their lunch. Then, well... it's best not to find out.