Most chicks hatch with yellowish legs. It's from the uptake of the yolk- IF I'm remembering correctly. It's very difficult to access leg color through photos. Too many variables. Lighting, pixels of the camera, pixels on the viewing screen, screen lights, and much more. Better to ask questions of the breeder and look at their breeding stock for the traits that you know to be true for the breed your looking to get. I breed purebred Ameraucana's and most of the chicks I hatch have yellow tinted Legs at first. It goes away as they age. If I had chicks that their legs actually started to look green as they age I would be concerned. Typically what I see is the yellow dissipates and then the slate blue gets darker, they don't darken together if that makes sense. But there is no way to know that through pictures of the chicks. You would have to look at the parents- AND remember that not all variety of Ameraucana are supposed to have slate/blue legs- it's dependant on the variety too.