And she probably will be a brunet the next time you see her walk the red carpet at the Oscars.
"First day on set for Z! She ain't a Duchess no more," the "Pan Am" alum wrote on her WhoSay account, sharing a photo of herself with messy brunet hair tucked under a "Co-Op Seeds" trucker hat.
The costumed look for Craig Zobe's "Z for Zachariah" is a huge departure from the Australian actress' look in "Wolf of Wall Street" and the now famous glamorous red carpet debut she made at the Golden Globes this month in a white Gucci column gown accented with emerald trim and accessories.
The sci-fi flick tells the tale of a post-apocalyptic teen named Ann Burden, who survives a nuclear war in a small American town. The film also stars "Star Trek" and "Jack Ryan" star Chris Pine and "12 Years a Slave's" Chiwetel Ejiofor.
Last week, the 23-year-old teased to her new hue on Twitter.
"Prep for Z for Zachariah is well and truly underway -- I'm now officially a brunette and spent the day milking cows and driving tractors!" she wrote.
It may seem that Robbie has become a force to be reckoned just out of thin air. But the truth is the actress, who starred in the Aussie drama "Neighbours," had been hard at work in Australia before making a splash stateside.
"It wasn't like, 'Guess I'll go to America!'" she recently told The Times' Chris Lee. "For two years while I was finishing my contract on 'Neighbours,' I was carefully setting things up. Two years of doing acting courses, dialect coaching so that I could have my American accent perfect. I didn't spend any money so if I didn't get a job, I wouldn't have to move back. Getting a team in place so I could get straight in the room with the best casting agents and not waste any time."
After a month in the U.S., she landed a role in the now canceled period drama "Pan Am" then later in the sci-fi romance "About Time."
"Everyone's like, 'overnight sensation.' It's not overnight. It's years of hard work," Robbie said. "I feel so fortunate that everything worked out according to plan. But it definitely was a plan."
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