Xanthoderma is a yellow coloration of the skin.
A xanthoma is a small, yellow nodule which occurs in the skin, which is rich in cholesterol and other lipids.
Yellow skin can mean many things. Yes many people will just think "oh someone peed on your skin..." well no. First it could mean ringworm. It glows a yellowish, greenish color under a black light. Another thing is ask your doctor! Or your turning into a Simpson ( Sorry couldn't resist putting that)