Michelle Williams bid adieu to the long wavy locks she's been sporting since last year: Today at Cannes, she debuted a dramatic new platinum pixie cut so cute it threatened to overshadow Blue Valentine, the movie she's there promoting with co-star Ryan Gosling. "We went for a [pale sandy blond] because she is playing Marilyn Monroe and we wanted to find a shade along those tones," Marie Robinson, owner of the N.Y.C. salon responsible for her new 'do, told us. "This shade works well on fine hair as it gives it tons of body. Michelle loves it!" It's not the first time Michelle's gone gamine—previous short cuts have included a honey-toned Mia Farrow-style crop and a golden chin-length bob. But the starlet's new style is significantly lighter, and features longer, side-swept bangs. "Jessica Gillin shaped [the super-short cut] so it could grow easily into a long layered bob," said Robinson. But it's not the easiest color to keep up: "You can play with the tones of these pale colors to make it work with any skin shade, but the maintenance is tricky. Don't bother if you can't be in the chair every four weeks—it looks trashy if you have too much root!" What do you think of her new pixie cut? Tell us in the comments below!