I've seen the improvements in our birds and it is going to take a while to get better size and type to be seen in the majority of the flock. But it's possible to make improvements and I'm happy with each bunch that gets some things improved, although sometimes in small increments. I think people just assume that crossing breeds will fix a flaw faster than good breeding selection will.There does seem to be a relationship between some few red feathers in the hackle of a black male and the green sheen. One of the biggest reasons that Orps and some of the other black birds have dull black is that many people think it is OK to use black birds that come from the blue matings. It is not the same black that produces greenish cast to black.
As Joseph says......the shape makes the breed. Some think it is okay to cross breed shapes to get bigger, deeper etc birds. Once you go away from the same shape of the breed, you are going to have troubles.
Walt