If one of the parents is recessive white, and the other a dark cornish, you can get black chicks.
All chicks from such a cross should be colored, unless the dark Cornish also carries a hidden single copy of recessive white. As to the chicks being black, that would be determined by what is hiding under the recessive white. You could get yellow chicks from such a cross if say it is silver columbian pattern under the recessive white, although I would expect some light back stripes to show from the pattern gene from the dark Cornish's double lacing.