Where did you get them? If they were from a hatchery then we can assume they are pure breeds or recognised hybrids. If they are from some other source then possibly or likely mixed breed birds in which case we will be struggling to identify what the parents were especially if they were also not pure bred. Don't get me wrong, I love mixed breeds and farm yard mutts but figuring out their parentage if you don't know at least one parent's background is nigh on impossible.
It also looks like you have at least 2 cockerels judging by those thick red combs.
I'm fairly confident that, if those are purebreds, they are Jubilee Orpingtons.
I've raised well on enough mottled chicks by now to know a mottled when I see one. And the red is obvious.
Red columbian + Mottled = Jubilee
White legs + clean legs + light down = Most likely Orpington.