The 35-year-old singer showed off her fiery new locks at the "She's With Us" concert in Los Angeles, which raised funds for Clinton ahead of the California primary.
The former Voice judge shared a photo of her freshly-dyed hair on Instagram and captioned the picture with a lipstick kiss emoji. She is best known for wearing her hair in a platinum blonde shade.
Aguilera performed a medley of songs at the concert, where Ricky Martin, John Legend and Stevie Wonder were also present. She praised Clinton as "the ultimate fighter" before closing her set with her song "Fighter."
Aguilera hosted a fundraiser for Clinton at her Beverly Hills home in November. Sources told People the singer considers the politician a "strong female role model" and "a tireless advocate for everyday Americans and their families."