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Everybody knows about the pink nipple test for whiteness. Here's a way to determine if someone is white without having to ask them to show you their nipples. Melanin in the skin has an optical effect like melanin in the eye does. When there is an absence of melanin in the skin, veins will appear blue similar to how when there is an absence of melanin in an iris the iris will appear blue. When there's melanin in the skin veins will appear green until the skin is so dark that you can't even see vein colour.
