Judas
Obviously, we'll never know if Judas Iscariot, the Apostle who famously betrayed Jesus Christ in the Bible for 30 pieces of silver, was actually a redhead. But he is often portrayed in medieval paintings as having flaming hair and an equally crimson beard. The phrase "Judas color" was used to refer to red hair, and no less a personage than William Shakespeare made reference to it, in As You Like It. ("His very hair is of the dissembling colour, something browner than Judas'.") In a grand irony, the depiction of Judas as having red hair — believed to be partially a function of needing to make the traitor stand out from the other Apostles in paintings — has contributed to several centuries' worth of discrimination and negative attitudes toward redheads.