There is no known combination of the colors ro produce that color because that color is a skin deficiency to give it the blue color we all pitbull owners love...I have seen a lot of blue come from white and a dark color rather it b brindle straight black or what ever, butthere is no way to guarantee your going to get a blue one and even if ou did, theres no gaurantee its going to keep its hair...with the blue color being a deficiency it is prone to lose all its hair if not took care of until the dogs about 6 months old, I hope this can answer your question..
