Hope this isn't hi-jacking the Breeders thread...
Select juveniles that do not have dark black legs...some can have yellow under black or willow legs. Breed these to a good yellow leg and select for yellow legs.
I have LF Columbian Wyandotte, as well as a project pen of Birchen Wyandotte that is not an accepted color variety yet. Limiting hatch to 50 chicks from each pen.