Jessica Alba is losing her hair (color) in her quest to prepare for her return to Sin City…

The 31-year-old half-Mexican American has revealed her transformation back into her Sin City character Nancy Callahan via her Twitter and Instagram accounts.

Alba—who is returning to her iconic role for the sequel to the cult classic, which is being called Sin City: A Dame to Kill For—shared images of her blonde transformation.

“”Bye Bye Brown Hair” r u on viddy yet? I’m documenting my brown to Sin City blonde!” wrote Alba before getting her makeover.

Alba later followed up with more photos that showed her during the hair coloring process. Once she completed her transformation, she shared a photo of herself with her newly-lightened locks and wrote,

“She got roots that Nancy #sincity2.”

But Alba isn’t just changing her hair color… She’s also getting physical for the role.

The following day, Alba shared a photo of herself during training lessons at the gun range.

“What a way to start the day -training for a movie is sorta fun,” she announced.

Sin City: A Dame to Kill For will focus on earlier story of Clive Owen‘s Dwight McCarthy, whose life is turned upside down when Ava, a woman from his past, returns and causes all sorts of problems for him.

Directed by Robert Rodriguez and Frank Miller, the film is slated for an October 4, 2013 release.

Alba’s co-stars include Mickey Rourke, Rosario Dawson and Michael Madsen.