Once upon a time, there was a red crayon that could only draw blue: blue fire engines, blue strawberries, blue hearts—all things we know to be red he could only draw in blue. No matter how hard the crayon tried, no matter how critical the remarks of others, the crayon couldn't behave in accordance with the label on his side.

"He was red, but he wasn't very good at it," Michael Hall explains in "Red: A Crayon's Story," a forthcoming picture book that reads like a fable of gender identity.

"I have a girl brain but a boy body," says a young child in "I Am Jazz," a picture book by Jessica Herthel and Jazz Jennings that came out earlier this month. In Shelagh McNicholas's sherbet-hued illustrations, Jazz looks like a typical girlie-girl who likes to dance and play princess dress-up with her friends. She is also genetically male.

It is not a wholly new thing for a transgender person to appear in children's books, but soon they will abound. Last February, Susan Kuklin's "Beyond Magenta: Transgender Teens Speak Out" brought a series of riveting first-person accounts of teenagers who are grappling—some successfully, some less so—with sexual dysphoria, or the profound dissatisfaction with the gender of one's biological DNA.

"I Am Jazz" was next and will be followed later this month by two memoirs for older adolescents that describe either side of the much-publicized romance of two transgender teens, Arin Andrews ("Some Assembly Required") and Katie Rain Hill ("Rethinking Normal").