The Palm Beach poultry club has a website on which there are some descriptions of breeds. The description I am criticizing here is the text given for Blue Andalusian (link to confusing discussion). The author says that the only way to get blue offspring (100%) is to breed a "white" Andalusian male to black females. He seems to be saying that the color-hybrid is then blue.
Splash white (BlBl) X non blue (bl+bl+) would be the cross that I would do to produce eggs or chicks for sale, but I wouldn't breed show birds like this. I don't see it mentioned by breeders, but I don't think that you can produce acceptable males and females in the same cross. Males seem to be too dark in lines that produce good laced females. To breed for the correct color blue you have to breed birds of the correct color together. If you breed a splash to a black you take your chances on what shade of blue you will be producing because you can't select for the blue color or the lacing in either splash or black.
First of all, it seems that the author believes that the white and black kinda "average" or "hybridize" to blue. He also seems to say that the male has to be the "white" one and the female has to be the black one.
Here is how it really works. Birds homozygous for blue (Bl / Bl) are splash or "blue-splashed white". Birds that are heterozygous for Bl are blue. (Assuming, of course that they otherwise have black plumage that can be changed to blue by the Bl gene.)
The "white" one (which should be called "splash" or something like that) is homozygous for the blue gene, Bl / Bl. This "white" Andalusian should actually be splash and not white, but this might be what the author refers to as "white" Andalusian. The black one is lacking blue, Bl, altogether, bl+ / bl+.
A cross between the splash ("white" in the text linked above?) Andalusian of either sex and the black one of the opposite sex gives the Bl / bl+ heterozygotes which are blue.
By Rokimoto on Sunday, January 20, 2002 - 06:00 pm: