french cuckoo maran

I bought 8 French cuckoo Marans from tractor supply. 3 are a dark black color and 5 are a light gray color. Does the color identify them as male and female? I know one already has a bigger comb than the rest and is more than likely a roo.

I was wondering what the chicks would look like if I crossed these two. I also could cross the blue Orpington with a sapphire gem but since the sapphire gems are so new I don’t think anyone has done that cross yet..