* The Arthurian Legends: The original Arthurian legends don't specify Guinevere's hair color.
* Adaptations: In different retellings and adaptations, Guinevere's hair color varies. Some portray her as a blonde, others as brunette, and still others as a redhead.
Therefore, you can imagine Guinevere with any hair color you like, as there's no "correct" answer based on the original source material.