Jessica Alba is going back to blonde.
The new dye job, which Alba chronicled on her official Twitter page over the past few days, is for the sequel to the 2005 film "Sin City," which is set to begin production soon.
Alba will be reprising her role of Nancy Callahan from the first film. Callahan is an exotic dancer working her way through law school. She was saved by Detective John Hartigan (Bruce Willis) when she was 11 from being murdered by a child molester. The two met up again when Callahan was an adult and Hartigan sacrificed his life to save her from being raped and murdered.
"Bye bye brown hair," Alba Tweeted on August 23 with a photo of herself in a hair salon. She later Tweeted a second photo that day with a caption that said, "Stage 1 -- ok it doesn't look that different but it's a process."
On August 25, Alba Tweeted a photo of herself with blonde ombre hair with her styling team in the background. "Stage 2 of 'Sin City 2' Nancy hair," Alba wrote.
Alba Tweeted the final photo of the process, which can be seen above, with the caption "She got roots that Nancy. 'Sin City 2.'"
On August 26, Alba Tweeted a photo of herself at a gun range with her new hairdo and said, "What a way to start the day -- training for a movie is sorta fun."
The 31-year-old actress has been blonde before for roles, including for the "Fantastic Four" films in 2005 and 2007, but has been a brunette since 2009.
Earlier this year, Alba launched an e-commerce company called Honest. It sells eco-friendly and toxic free family products.
Honest.com is named after the actress' daughter Honor, who was born in 2008, and offers monthly prescription packages for products like diapers, shampoo and laundry detergent.
Alba welcomed her second daughter Haven with husband Cash Warren in August 2011.