During her international promotional tour for The Girl With the Dragon Tattoo, Rooney Mara has stepped out in a slew of chic designer looks, but she's yet to wear anything other than black, gray or beige. Until now.

PHOTOS: Rooney Mara's incredible style transformation

The 26-year-old stunned fans on Monday when she arrived at the film's premiere in Rome, Italy clad in a vibrant red lace Valentino gown.Her hair, which she chopped off and dyed jet black to play a punk computer hacker in the flick, was pulled back showing off her dramatic, blunt bangs. "People always ask, 'Were you crying when they cut your hair?' And it didn't freak me out at all," she told the January issue of Allure. "I was really happy to do it."

PHOTOS: Biggest celebrity hair makeovers

And her onscreen character Lisbeth Salander left a mark on the actress' personal style, too. "I used to wear a lot of girlie, frilly things, now I buy things that are more comfortable, and more utilitarian, and sort of boyish."

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