I'm sure someone with more knowledge will correct me but.... Girls have one gene responsible for cuckoo and boys have two responsible for cuckoo pattern. You can gett non cuckoo patterned birds out of cuckoo pairing. (as long as your rooster isn't double barred) but if they don't show markings they don't carry the genes for it. Even if one gene is there it will show the pattern, and double barred trumps all, if you have a double barred rooster all of the chicks will hatch out cuckoo.
I'm not a genetics pro, but there is something in the genes for cuckoo that also restricts the black skin pigment. And everyone is working hard to get rid of this pigment color restriction.
It IS harder to get rid of the skin pigment problem in roosters than hens. But it happens in both sexes. I hatched out eggs last year from a breeder, some roosters ended up with fairly dark skin or at lest patches of black here and there. And my only cuckoo hen i got has bubble gum pink skin and comb. So it is not a sure way to sex them. Hope that helps