I have had hens set in the same box & I arranged the eggs so that the hatch dates were all due at the same time. Last year I had 2 Blue hens that hatched a mix of Blue & splash chicks, no problem both hens tended all the chicks (kept seperated from the rest of the flock until the chicks were about a month old & well bonded to moms & eating good) This year I had a Blue & a red hen that decided to share a box & eggs. It was very cold here during the brooding & the hatch was stagered over 4 days. I removed the Blue hen (older/experienced mom) & gave her the 1st 2 chicks so they could get started on feeding (both were splash chicks) when the remainder of the chicks hatched (all blues), I put the red hen in with the blue hen & all babies back together. For reasons I haven't figgured out, (about 5 days later) the red hen killed one of the splash babies & tried to kill the other one. Even though SHE is the one that hatched them, the 2 day gap must have caused her to "forget" or I am thinking possibly it is because they were a different color then "her" babies (she -the red hen, was a 1st time mom) In the end I removed the red hen from the pen & the Blue mama has the remainder of the babies - NO problems.
These chickens were all the same breed, just different colors. I assume chickens see colors, as other birds do. (anyone know for sure?) It would account for the red hens attack of the "different" babies.