White - Newbie (or pre-zedling): players who have spent <15 hours on the LVS server.
Yellow - Zedlings: Players who have spent >15 hours on the LVS server.
Pink - Zesties: Players who have donated to LVS server, they don't have to have become a Zedling before donating
Blue - Zriends: Players who are there to run certain community areas. The Market, The Nether Hub etc. They put the time to work on and run these areas, are both recognised for it, and given certain permissions to facilitate that.
Green - Guardians: The server's admin, who save us from horrible mean nasty griefers
Black - Jailed players: You wont see these players for very long before they are auto-banned. However this does not give you an excuse to be horrible to them as they may be in jail as a misunderstanding. They are people too, with feelings. Remember that.
Red - Speaker, zedwick has created a stick that changes your player name to red if you are holding it, this person is speaking on a matter at the council, it's always best to listen to what they have to say.
Hope that clears up any confusion!