One thing is for certain: no matter what hair style she chooses, Sienna Miller looks best as a blond. Sure she's tried different colors in movies; in Casanova she had red hair and in Factory Girl she was a brunette for about a second, but I really like her hair light and bright.
So it's really just a question about what style you like best on her. I am torn between her first look where her hair (although unkempt) is flowy, long and loose, and the last look where she's got a cute as pie pixie cut. Which hair style do you like best on Sienna?