Yes you would have to worry about skin and leg color in addition to comb. I am pretty sure that white skin/legs are dominant over yellow. As far as the comb goes you would have to breed that out in time. About the single combs from wyandottes, I was on another forum and a couple breeders I talked to had said that they have never gotten single combs from their chocolate wyandottes and I was realizing that when I still had the solid dun birds I had a few people ask for single combed sports so they could make dun cochins and dun ameraucanas and such since the single comb is recessive but in the 3 years we had them we hatched out many many chicks and never got a single comb and the person we sold them to said the same thing, no single combs. So once you get the single comb into them than it is more likely to show up.