Alba goes blonde for Sin City 2

Jessica Alba has dyed her hair blonde for the Sin City sequel, A Dame To Kill For.

The 31-year-old actress posted a series of photos on her Twitter as she embarked on her transformation from brunette to blonde as she prepared to reprise her role as stripper Nancy Callahan in Frank Miller and Robert Rodriguez's follow-up to the 2005 neo-noir crime thriller.

"Bye bye brown hair," she wrote on August 23, later adding: "Stage 1 - ok it doesn't look that different but it's a process."

On August 25, she posted another picture of her lighter locks with her style team at Robert Ramos of Estilo Salon in Los Angeles posing in the background.

"Stage 2 of Sin City 2 Nancy hair. She got roots that Nancy. Sin City 2," she wrote.

With her new hair colour in place, Jessica hit the shooting range on August 26 to practise her skills.

"What a way to start the day - training for a movie is sorta fun," she said.

Clive Owen, Mickey Rourke, Rosario Dawson, Devon Aoki and Michael Madsen will also return for the eagerly anticipated sequel, which is based on Frank Miller's graphic novel series.

Sin City: A Dame To Kill For is scheduled for a 2013 release.