© @Copyright HELLO! Hello! Magazine is renowned for her , but the No Doubt singer has enjoyed experimenting with many different looks over the years.On Saturday, the mother-of-three celebrated her 51st birthday, and shared a number of of herself on Instagram, including a collage featuring pictures of her .The singer's hair was styled in a number of different looks, Gwen was also photographed with a mullet in , of the star on stage with Sting.The image was taken when The Voice star was a