Q: When is a black eyed white not a black eyed white?
A: When it’s a “very pale creamy white” rather than just “as white as possible”.
In reality, there’s little to pick out colour-wise from an ivory and a black eyed white, with one being white and the other being milky white. The main difference would be found in the hair on the ears, which can be darker coloured in an ivory, while it would be white on a BEW.
Breeding-wise, there’s lots of differences. Ivory bred to ivory will produce mainly (or all) ivories, and they can be outcrossed to any other variety with black eyes and then crossed back to ivories without affecting the colour. This means they tend to be quite strong and robust rats.
Genetics: albino with at least one copy of the black eyed gene (Be-cc)
NFRS Standard: Body colour to be very pale creamy white all over with no odd coloured hairs or patches. Ears and tail to be pink. Eyes black.