I think the composites look just a bit off from actual bone. while this may be hard to see at home in your mirror, they are using a more direct source of light in your mouth. I can tell the difference on my teeth, again it is only slight. Probably depends on the natural color of your teeth. I do know that some composite materials show up on x-rays as they have a bit of metal in them for this purpose. I have seen the bonding on my front teeth on x-ray. This question any dentist should be able to shed more light on.