Yes, it's a feature of colored egg layers except for pure blue egg layers. The tint is laid down after the shell is formed, and depending on stress factors and other conditions, the egg may vary in tint intensity and smooth appearance of the color. Freckled eggs on occasion is one of the charming things about getting colored eggs.
Did you know, by the way, the color laid down in tan eggs, red eggs and brown eggs, as well as olive green eggs from EEs, is formed using spent red blood cells? Deep red and chocolate brown eggs have such a thick layer of these red blood cells on them that you can easily rub it off. In fact, I've seen what appear to be scratches on the "paint" from debris on the hen's butt caused by passing through the crusty butt feathers. It's one reason I try to keep butts clean with occasional butt baths.
