Rachel Bilson became a redhead! Well, temporarily at least. The actress donned a red wig on the set of her new Magnum commercial, which she filmed with Chanel designer Karl Lagerfeld, and you can see a sneak peek of the look in this new behind-the-scenes photo. Isn't it fun to play dress up once in a while? See more celebrities who love colorful hair in InStyle’s Rainbow of Star Hair Colors.