I have Cuckoo Marans and I raised them from chicks. My question is some are dark almost black are those hens? because the ones that look similar to a barred rock look like roosters and are lighter in color.
Hard to say without pics, but all my female Cuckoo Marans were darker than the cockerels, even as chicks (McMurrays). Once they're a few weeks old, the differences become pretty obvious. All of mine were fast developers.
You have a definite roo on the left and pullet on the right of the pic. Often, yes, the pullet is darker. But also note - The cockerel has very large, red, fleshy looking comb and wattles.