This collection of Marans is extremely rare and may include any of the following breeds: Black Copper Marans White Marans Golden Cuckoo Marans Blue Splash Marans
Most of them will get the cuckoo coloration (ones with the spot on their head). The dark one will be your black marans. The white ones are your white marans.
It's hard to tell from those pics, honestly. The cuckoos should be golden if that's all that's offered in the order. The whites COULD end up splash, but I'm not seeing any flecks of color on them, so it's doubtful. But again, the pictures aren't that close of the whites, so you could see splashes and flecks that we can't.
The head spot chick (are both pictures of the same bird or did you get two like that?) is your golden cuckoo, the dark chicks without head spots are your black coppers, the light ones are white Marans. I don't see any blue splash but 3 out of 4 is great for a small order!