The 20-year-old is a natural blonde, but has dyed her hair auburn for her role as Sansa Stark in Game of Thrones, an important character detail so that she resembled her mother Catelyn on the show. However, it looks like between filming the star has opted to change her look, and showed fans a glimpse of her new, bright blonde locks on Instagram.
CLICK TO VIEW GALLERY
Sophie dyed her locks bright blonde
In the snap, only half of Sophie's face is visible as she showed off her new hair colour, and captioned the photo: "I did a thing," accompanied by an emoji.
Fans of the actress were quick to voice their opinion on her bold new look, with one writing: "it's stunning," while another joked: "Don't tell me you're a Targaryen too," referring to a character with white-blonde hair in the fantasy TV show.
Sophie isn't the only Stark actress to try a hair change in between production, as her on-screen sister Maisie Williams has also tried out a new look, turning her brunette bob blue.
Sophie is known for her red hair
The hairstylist who dyed Maisie's tresses, Seniz Alkan, revealed how she created the look so fans could try at home. She said: "I ombréd Maisie’s hair first with two scoops of Platinum Plus by L’Oreal, with 6 per cent left it on for 20 minutes to lift the hair.
"After washing it off with L'Oréal shampoo, I then put a mixture of blue Crazy Colours - Capri Blue and Peacock Blue into the sections and left it on for 15 minutes, before rinsing and put a Masquintense mask from Kérastase in to give it some gloss."