In Reservoir Dogs, each of the crooks are given a colour based pseudonym, but aside from enabling a funny argument when the names are being handed out, I don't really see the point.
The idea given is that of they don't know each other's real names, if any one of them is collared, they won't be able to identify the others when questioned.
But they all know Joe and Eddie, the ring leaders, who the police would surely be most interested in, so what's the point? Is Joe just that considerate of his employees that even if he gets caught he doesn't want them to rat each other out?