Blue Black and Splash colors all breed together in 1 pen and you can get all 3 varieties. the "color" Blue is a diluting gene,so if your bird is....
Black = 0 copies of blue
Blue= 1 copy of blue
Splash 2 copies of blue (1 from each parent) in other words you will not get Splash from just a black and blue as each parent must have at least 1 copy of Blue.
We are just starting our BBS pen so it is still "a work in progress"