Looks like a joke, but this just might be worth a try. This rainbow challah was created by a Jewish culinary maestro by the name of Amy Kritzer. She used natural dyes including pomegranate juice, beet juice, harissa, paprika, turmeric, spinach, red cabbage and blueberries. But it takes a lot of work to pull it off -- not for the uninitiated or if you're pressed for time.
Kritzer has a refreshing Jewish culinary blog called What Jew Wanna Eat.