As a human, he has brown hair and (usually sad) brown eyes. At the beginning his hair is cut in a more Mohawk style, but by the end it is longer, as by that time he is in turmoil (and it is represented by his appearance when he begins to grow a beard and longer hair). As a Na'vi he looks like himself but with Na'vi touches- blue skin, cat eyes, a flatter nose, etc. Avatars are more human than natural Na'vi, with more ridged noses and 4 finger instead of three. For more info, visit the Avatar page.