I don't know if this will help you but it is what I have saved on blues taken from different breeders here on the BYC:
Blue X Blue does not give 100% Blues
Actually this is the way their matings go:
Blue X Blue = 50% Blue, 25% Black , 25% Splash
Blue X Splash = 50% Blue , 50% Splash
Blue X Black = 50% Blue, 50% Black
Black X Black = 100% Black
Splash X Black = 100% Blue
Splash X Splash = 100% Splash
Only way to hypothetically get 100% Blue, is to do Black X Splash.
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silkied splash x silkied splash = 100% silkied splash
silkied splash x smooth black = 100% smooth blue, carrying silkie gene
silkied splash x smooth blue = 50% blue, 50% splash, with 100% smooth feathered, carrying silkie gene
silkied splash x f1 black = 100% blue, with 50% smooth carrying the silkie gene, 50% silkied
silkied splash x f1 blue = 50% blue, 50% splash, with 50% smooth carrying the silkie gene, 50% silkied
f1 blue x f1 black = 50% black, 50% blue, with 25% smooth and not carrying silkie gene, 50% smooth but carrying the gene, and 25% silkied
f1 blue x f1 blue = 25% black, 50% blue, 25% splash, with 25% smooth and not carrying silkie gene, 50% smooth but carrying the gene, and 25% silkied
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Cross her(Black Mottled D'Ucccle with a black roo = F1 offspring that are black
Back cross a black F1 male to his mottled mother= BC1 offspring which will be black or they will be black and mottled.