i might guess they could be self blue, but without seeing the actual feathers, you can't always go by fluff color i think...My laptop is in the shop... But here is a link to a pic of my new babies on photobucket. These are from the black hen and black roo.... Blue, right? 4 blue one black?
Beth
There is nothing you can mix to make Self Blue except Self Blue. No amount of mixing Blues will make Self Blue. A different gene(lavender) is required for Self Blue.
but she already said the parents of the chicks are both black... and the only way to get anything even remotely blue from 2 black parents is self blue, since it's recessive, not dominant. unless one or both of the parents are DARK navy blues and not really blacks maybe?
You said the parents of your Black Rooster were both blue. As far as self blue. It is possible to have F1 blacks from a self blue x Black. Then when the F1 blacks are bred back to each other you would get some self blue 25%, 50% black not carrying the gene and 25% black that carry the gene probably. If the chicks feel are yellow you probably do not have self blue. When in doubt just let them grow up and the answer will come in time.
Hens go broody when you don’t want them to… and won’t go broody when you do. 
