Sienna Miller has rarely experimented with her trademark blonde tresses, so she surprised fans when she unveiled a new auburn hair colour on Tuesday night. The 33-year-old made a rare official public appearance as she celebrated the launch of sister Savannah's new collection for Debenhams, looking virtually unrecognisable with her dramatic new makeover.
Sienna Miller unveiled her new auburn locks on Tuesday evening
Looking every inch the style icon, Sienna complemented her new 'do with her effortlessly cool personal style. The star rocked an oversized grey jumper from Savannah's new collection Nine by Savannah Miller, which she teamed with black skinny jeans and accessorised with a pair of tan suede peep-toe boots.
The American Sniper star hasn't just ditched her blonde locks in favour of red hues because she fancied a change – the bold new look is part of her makeover for her latest role in upcoming movie The Lost City of Z, which she is currently filming in Northern Ireland.
However, Sienna made sure to take time out of her hectic work schedule to come to London and support her sister at the glamorous launch party held at London's trendy Ham Yard Hotel.
Sienna supported Savannah who is launching a new collection for Debenhams
Savannah recently revealed exclusively to HELLO! Fashion that she turned to Sienna for advice when she was creating her new designs, as she joins the Designers at Debenhams line-up.
"We do that anyway because we're sisters and best friends," she told us. "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 admitted that while the stylish siblings talk about fashion, it's something they rarely talk about nowadays.
"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."
