The dots beside a user name denote whether a person is online or offline. If you are offline, the dot will be grey. If you are online, the dot will appear yellow.

The dots also denote a members status:
Plain grey: regular member offline
Plain yellow: regular member online
EX: core

Blue/grey: offline mod
Blue/yellow: online mod
EX: SidneyStrange

Green/grey: offline developer
Green/yellow: online developer
EX: bro

Pink/grey: offline Supermod/Admin
Pink/yellow: online Supermod/Admin
EX: lyiint

Grey fried egg: offline retired mod
Yellow fried egg: online retired mod
EX: LaughingCrow