The blue can comein many shades, I prefer the two extremes, the dark, almost black, blue, an the pale, almost looks splash but its the same color all over so it not, blue. I have 5 Blue cochin chicks in the brooder and they are all a different shade.
I think it happens more when the parent...
Black x Blue = 50% black, 50% blue
Blue x Blue = 50% blue, 25% splash, 25% black
Blue x Spalsh = 50% blue, 50% splash
Splash x Splash = 100% splash
Splash x Black = 100% blue