The 25% blacks that came from the blues will always continue to carry the blue gene and if bread with a black Sumatra hen that carries the blue genes they can throw blue chicks. I know this for a fact because I have that problem I bread my blacks and have blue chicks from them
Not necessarily from the previous mate, she may have bread with a black Sumatra, but that does not mean that the black Sumatra does not have the blue Jean when you cross two blue Sumatra 50% of your hatch will be blue 25% will be black and 25% will be splash. It is very possible that your...