What color is Gemini hair?

Could you please clarify your question? Gemini is an astrological sign, not a physical entity with hair that can have a color. Perhaps you are referring to a character or entity named Gemini from a specific piece of media or culture, in which case the answer would depend on that specific context. However, without that context, it's not possible to provide a definitive answer to the question "What color is Gemini hair?" as it doesn't make sense in the context of astrology.