Blue is the Warmest Color by Jul Maroh

Blue is the Warmest Color is a graphic novel about growing up, falling in love, and coming out. Clementine is a junior in high school who seems average enough: she has friends, family, and the romantic attention of the boys in her school. When her openly gay best friend takes her out on the town, she wanders into a lesbian bar where she encounters Emma: a punkish, confident girl with blue hair. Their attraction is instant and electric, and Clementine find herself in a relationship that will test her friends, parents, and her own ideas about herself and her identity.