There are only 2 colors that go all the way through the shell to the membrane and that is the blue and the white, all other colors are added by the hen during production from pigments/due that is either in her blood or egg production equipment. I have red this more than once, so every time we crack an egg, we look on the inside for evidence that this info is wrong, so far it has held correct, all shades of brown, cream, tan, and green eggs so far, naturally we aren't checking white eggs.

I looked this up awhile back when I decided to breed for color and what went with what to make what ever.