Star’s are a good indication for how much experience you have. As you know, all players start off with light blue star and their color progresses with how much stars they have. Players gain these stars by how much fame they get, which correlates to how long they live. This game, in simple terms, is to know what kills you and what does not (i.e. FFA tombs on a melee vs. clean tombs on a melee, having good pet vs. having bad pet). Once you figure that out, you have more experience in the game to know how to keep your precious characters alive. More experience = more time alive = more fame when they die = more stars = different star color.
Of course, about anyone can hop on the ptrain and get whatever star color they wish, and some people (liek m3) are alts. So keep this in mind when you judge someone.