Sex linking silkie crosses

[Athenax79]

I'm trying to understand this correctly. I have a silkie hen that bred with a white rock. We have two offspring. One with yellow shanks and one with black shanks. I'm assuming from what I've read that the yellow shanked chick is a hen. Is the black shanked chick a rooster? Both seem to lack black skin. I'm not sure if this matters as I'm a bit confused to the Fm id+ relationship.