Splash is two copies of the blue gene: Bl/Bl. Blue is one copy of the blue gene: Bl/bl+ Not-blue is zero copies of the blue gene: bl+/bl+. I do NOT call this black, because it is not necessarily a black bird. The colour of the bird is determined by a large number of genes. Blue is a diluter of black pigment. Not-blue means that any black pigment in the bird is not diluted by the blue gene.
(b is not-barred, a sex-linked gene; B is barred, the incompletely dominant allele.)
(b is not-barred, a sex-linked gene; B is barred, the incompletely dominant allele.)