If those are purebred Brahmas, their colors aren’t standard. Only buff, light, and dark colors are accepted in the US, and none of the four have these colors. Your two full grown hens look like partridge and lavender, which are accepted colors in other countries, just not here. The two young ones are black and either white or lavender, which also aren’t standard. They do all look like purebred Brahmas, though, with pea combs, feathered feet, and a beetle brow, which is what makes them look mean. As for gender, it’s a little early to tell, as Brahmas are notoriously slow developers.