Sienna Miller is now a redhead, talks about her year's highs and lows

Sienna Miller traded her signature blonde locks for a fresh auburn 'do, surprising fans on Tuesday night as she celebrated the launch of sister Savannah's new clothing collection for British department store Debenhams.

Looking virtually unrecognizable with her dramatic new makeover, the 33-year-old actress showed off her new look with an over-sized grey sweater from her sister's new collection, Nine by Savannah Miller and teamed it with black skinny jeans and a pair of tan suede peep-toe mules. The bold new look is part of her makeover for her latest role in the upcoming movie The Lost City of Z, which she's currently filming in Northern Ireland.

Sienna Miller helped her sister debut her new clothing collection for a British department store Image: Getty Images

Despite her busy schedule, the Mississippi Grind star still makes plenty of time for family. Savannah recently revealed exclusively to HELLO! that she turned to Sienna for advice when she was creating her new designs. "We do that anyway because we're sisters and best friends," she said. "I did ask for her opinion about certain things. She always is in agreement, and I really respect her style."

The mother of three also said that fashion now takes a backseat to their other important role as mothers. "We don't really have time for that, being mothers," she admitted. "Neither of us spend hours discussing our style at all, it's more about what we like and wearing things we like."

Sienna took a break from filming in Northern Ireland to support her sister, Savannah Photo: Getty Images

Sienna recently opened up about the “curse of motherhood” in an interview with British Vogue. She appears on the magazine’s October cover. Daughter Marlowe was born in 2012, six months after the actress announced her engagement to actor Tom Sturridge. The two split this summer.

"It's been really quite overwhelming recently, just with the volume of everything going on," she explained. "Everything is shifting. It's actually been the s---tiest year, and amazing. It's always yin and yang. I feel like if you're excelling in one area, it's hard to manage both, and I do feel like the work is going really well."

Sienna opens up about motherhood in the Mario Testino shot issue

For the British beauty, she has had success after success starting with Fox Catcher and American Sniper and has several more movies set for 2015. "Obviously when you have a baby it's the most incredible experience but your life is also catapulted into this chaos and you are exhausted. I could literally get on this table and fall asleep," she continued. "I'd like to be better at managing things; I'd like to be more super — although we're never going to feel it, even if we are. That's the curse of motherhood — we just run ourselves ragged. I'm just trying to get a sense of what that guilt is. I sometimes feel like it's a totally invented emotion. It's strange to be punishing ourselves this way. It's not healthy."

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