The chocolate gene in the Orpingtons in England are sex linked. It is not a dilute/double dilute deal like blue and dun. You either have it, (in the males) or you don't. If the male is black, it does NOT carry chocolate unless his mother was chocolate. If his mother was chocolate, he is guaranteed to carry it.
If a black hen had a father that was chocolate, she will for SURE carry it, and only pass it on (visually) to her male offspring. I believe half of her female offspring will not show it but they will also carry it and pass it on visually to their male offspring, and will have a fifty fifty chance of chocolate genes passing on to each of their female offspring.
If you breed a chocolate roo to a chocolate hen, everything will be visually chocolate, with the sex linked chocolate orpington gene anyway.
Edit, OOPS! Second half of the first statement is wrong. If the rooster is black, he does NOT carry it!!! This part of my statement is NOT TRUE! Please ignore!!!
"If the male is black, it does NOT carry chocolate unless his mother was chocolate. If his mother was chocolate, he is guaranteed to carry it. "
The truth is, if his mother carried chocolate, he would BE chocolate. Black males cannot "carry" chocolate! Sorry for my mistake.