Feel free to correct me if I'm wrong as I certainly don't come anywhere near to specializing in these colors, but if your Black is from a black X blue mating, it carries the blue gene. The Splash is from a blue X blue mating. Put them together and you'd have a chance at blue, black or splash chicks. Only a pure black (from black X black) mated to a splash will produce all blues. Did that make sense?
Jody
Jody