I asked Mcmurray Hatchery if their dark cornish and white rock feathers are the dominant type. I still waiting on reply. They usually answer my questions with in a week.
If you have a dominant white rooster crossed with a recessive black hen all the babies should turn out white. However, if the rooster and hen both have dominant color you are going to get a mixed looking chicken. Then if the mixed babies are bred together there will be 25% white, 25% black, and 50% mixed. I found some info on Google search, but can't remember link.
I think if you let the cornish cross eat their fill in the morrning and then take away their feed, they should survive. I started an experiment with my 6 week old cornish roosters from Mcmurray hatchery. I took away their feed this morning when they stop eating. I'll put the feeder back this after noon and take it out after they are done. I have two of them, right now they eating about one and a half pint of crumble morning to evening. Hopefully they will end up eating less by feeding twice a day, I may end up feeding them once a day, it depends on how they look. Right now they look too FAT and bald.