Somewhere I read that Andalusian Blue is a seperate gene and has to already be present. However, I have personally gotten blue chicks out of a black and white mating when I was in 4-H. I have a black silkie hen that was in with a white cochin, and I got a freaky looking smooth feathered BLUE pullet out of that clutch-actually turned out to be one of my favorites of all time. There were NO blue or splash chickens anywhere on or around the property, though it is possible the silkie hen was two-timing her man...