* Ancient Greek sources: Ancient sources don't always explicitly state the color of Persephone's hair. She is associated with springtime and blooming flowers, so it can be assumed to be fair.
* Modern interpretations: Modern interpretations differ wildly, with everything from blonde, brown, black, and red hair.
So, there's no single, definitive answer to what color Persephone's hair is. It's open to artistic interpretation and storytelling needs.