Erudites were the researchers, law makers, and governing body
Dauntless were military and law enforcement
Amity were farmers and producers
Abnegation doesn't seem to be really necessary, but seem to be a Peace Corps equivalent, or shelters or charities
Candor? Were they some judicial branch?
ORANGE for all
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Abnegation were the governing body; Erudite fomented a coup to replace them.
Candor were the judicial branch--though we're never actually shown them acting in that capacity.
That actually just came up in Insurgent where I'm reading right now. During a meeting between faction leaders, Candor is told,
...you are the only disposable faction. Candor does not provide us with protection, sustenance, or technological innovation. Therefore you are expendable to us.