6. Amy Adams
Natural hair color: Strawberry blonde
Why she went red: She dyed it for Dr. Vegas, a TV show starring Rob Lowe that otherwise had no lasting influence. "I played a nurse and there was this beautiful blonde, Sarah Lancaster, who was cast as the casino dealer," Adams recalled for Backstage. "I'm in a room with her, and they said, 'Someone's going to have to change their hair color.' She's tan with these beautiful lioness green eyes and this mane of blonde hair. And I looked at her and me, with my pale freckles, and thought, 'Gee, I wonder which one of us is going to go red!'"