another suggestion, and I have found to be effective when determining blue or black, is to breed to a splash. If hes black you should get 100% blue and being bred to splash will lighten the blue tone a bit. When bred to a black, if it is a very dark blue, can deepen the blue color more and make it hard to tell on the offspring. If not 100% come out blue, then you know you have a blue.
If a Splash chick pops up out of this mating then the rooster is blue.
