So "assorted rainbow layers" is fancy way of saying mixed breed with colorful egg laying genes in there. They're also sometimes sold as Easter Eggers, but EE generally have muffs and beards and that's a whole other weird breed train to go down as far as what's an EE and what's not.
I'm not at all capable of guessing mixes/colors from chick down unfortunately, but they look cute!
It depends on the hatchery. Sometimes they sell rainbow layer assortments so you get a variety of egg colors, not necessarily all blue and green egg layers.
That said, these look a little off for barred rocks or cuckoo Marans, so they may well be hybrids of some type.