I'm not too familiar with wyandotte combs, so not sure how hard that would be to work with since orps are single combed. I know both rocks and wyandotte are yellow skinned and orps are white skinned, so that would take a little extra to work out and get right. Not impossible though, as we had the same issue with araucana when we first obtained stock and have successfully achieved yellow skin on our birds over the years. You just have to select for it along the way, as well as the other breed characteristics you're working on.