Those are helpful articles, though I did not read quite all of the second one. So I'm not sure if it goes into the fact that birds can be both dominant AND recessive white, since they are altogether different alleles. We have some examples of that in White Chanteclers. Folks breeding white to white can't understand why they sometimes get color appearing. Brother Wilfrid used both White Leghorns (dominant white), and White Rocks and White Wyandottes (recessive white) to make his creation. So if a mating were made whereby both parents were hetero for recessive white, some chicks could appear with red/buff feathers. Likewise, if chicks were produced with only one copy of recessive white and one copy of dominant white, it might allow leakage of some black or gray feathers as well. Hopefully all our Ameraucanas are recessive white only, but if you get some surprises from white to white matings, this might be one explanation.