are they chrome covered pickups?
because if they are, then the bare wire is most likely the shielding wire which go connect to ground (ie. back of a pot)
as for the red and white wires. one would be for signal(or positive lead), and the other one would be your pickup ground wire(or negative lead, which connects to ground). It would depend on the brand of the pickups. Certain guitar pickup companies use certain color codes for their wires. If you know the brand, then you can probably look it up.
But if you don't know the brand or its some random aftermarket brand then do trial and error, swap them back and forth and see/hear which one sounds better. lol
But my guess, its likely the red wire is for the signal, whereas the white wire is for ground.