It's quite simple - green includes Tac Vest and it's derivatives, up through heavy suit, blue is the gals' version of carapace armors, adding more protection and in some cases firing bonuses, and red is saved for the best conventional armors, only really two of those though. There are metal/grey armors for melee, and you could say that camoflage counts as color coordination, but most of the rest of the armors just do their own thing.