The 32-year-old actress shared a photo of her new look on the image sharing site Instagram on Sunday.
"#victoriaknox #selfie @barelylethalmovie taking a break btwn takes -hiding out in a rm -all this #action and #stunts r exhausting," she captioned the pic.
Alba had previously gone blonde for her role as Sue Storm in the Fantastic Four films. However, the Hones Company founder was back to looking like her old self Monday as revealed by a few other Instagram pics.
Barely Lethal, a film about a teenage assassin looking to have a normal life, will hit theaters in 2014.