Ya, Old English as Bred and Shown in the United States by Fred Jeffery and Bill Richardson has a lot of genetic information in it. It's about old English, but I think a lot of the info translates to other breeds.
I just saw that your from palm dale, is that palm dale Ca? I went down there to...
probably unless your birds are carrying a lavender gene. I think lavender is a further dilute of black that might come out if you breed your splashes, but don't quote me on any of the lavender stuff because I may be wrong.
This is because blue is acutely a dilute of black if you breed Blue to Blue you should get 50% Blue, 25% Black, 25% Splash, to get 100% blue you need to breed splash to black. Here's a chart
Blue X Blue = 50% Blue, 25% Black, 25% Splash
Blue X Splash = 50% Blue, 50% Splash
Blue X Black = 50%...