The new look is no accident as Sweeney is promoting her new film, Christy. Her colorist, Jacob Schwartz, told Vogue that the actress wanted to have some change in her look.
"Sydney was looking for a change and wanted to have a big hair moment for the red carpet to support her new movie, Christy," says Schwartz. "It felt like the perfect time to do something bold."
While Sweeney has always been blonde, Schwartz shared that she was previously more of a "suede blonde," and her hair color is now brighter.
"It's more of an icy blonde," Schwartz adds. "The color really makes her eyes and features pop and complements the cut so well."
In Sweeney's latest release, the actress portrays former professional boxer Christy Martin. The film goes over Martin's rise to fame in the 90s, her tumultuous relationship with her ex-husband and manager, as well as sexuality, identity, and survival.
"I absolutely loved it," Sweeney said per Deadline. "I truly felt Christy's power as I transformed. And I really enjoyed being able to train and work with incredible boxing coaches and weight trainers, and nutritionists that helped me get to the place that I was for Christy."
The film also stars Merritt Wever, Katy O'Brian, Ethan Embry, Jess Gabor, Chad Coleman, Bryan Hibbard, Tony Cavalero, and Gilbert Cruz.
Sweeney also revealed that she had to go through a physical change in order to portray Martin. The Euphoria actress had to excessively train and gained 30 pounds in the process.
"I had a nutritionist work with me as well as a weight trainer and a boxing trainer," Sweeney explained during an interview at the Variety Toronto Film Festival Studio. "We upped my calorie intake, and I started taking a lot of protein shakes and supplements and eating everything. I ate a lot of Smuckers, a lot of PB and J sandwiches, milkshakes, kind of just constantly always eating because we were so active. I was constantly burning it all off at the same time. So keeping it all up was quite a challenge."
Being prepared physically for the role was half the battle to portray the boxing aspect of the part. However, Martin's story about her personal life, having had a near-death experience at the hands of her ex-husband Jim Martin is a pivotal point in the boxer's journey to greatness.
"I'm just glad that Christy's story is out there," Sweeney said.