I don't honestly think that feather color has anything meaningful to do with how cold-hardy a chicken is. First, it is only relevant at *all* during the daytime, which is not when your really cold temperatures are; second, up here there is little enough winter sun (low and brief) that dark...
Buckeyes and Chanteclers are the two (north american, anyhow) breeds developed specifically for frostbite-resistance and vigor in the cold.
I have three (formerly four, et one, he was *unusually* tasty) Buff Chanteclers. They are very nice birds, I like them a lot personality-wise. However the...