Phil,
The males, especially, may look brassy until the pin feathers all grow out, particularly in the hackle. Not much you can do about that - short of cheating. The best bet is to let them fully feather, give them a decent bath, and let the chips fall where they may. If they have the proper genetics they won\'t be brassy. Proper genetics include E or E>R at the e-locus, (S) silver instead of (s) gold, Bl/BL (blue), and possibly a few others. Sometimes you can get better whites by crossing them with blacks to introduce E at the e-locus, but of course that takes two generations.