Sienna Miller once turned her hair green when she tried to dye it brown.

The 'G.I. Joe: The Rise of Cobra' star - who is expecting her first baby with boyfriend Tom Sturridge - tried to change her blonde locks to brunette using henna for an audition but suffered a hair disaster.

She told the Daily Mirror newspaper: ''I've had some real hair disasters. I once used henna to dye my hair brown for an audition thinking I was being clever as it's natural.

''Little did I know it was the worst thing I could have done as it coats the follicles so that nothing else can penetrate.

''I had to put ketchup in it for about a year to get rid of the green tinge.''

Sienna, 30, and Tom, 26, recently went on a ''babymoon'' to Portofino, Italy and Sienna - who has recently gone brunette again - has ditched her usually glamorous look for more comfortable attire.

A source told Closer magazine: ''The babymoon has been planned for months. Sienna wanted to completely wind down before the birth, eat good food and go somewhere so chilled she didn't have to feel like she needed to dress up and make an effort.

''They're so happy and it shows in Sienna's appearance. She's so comfortable with Tom and feels she can really be herself with him.

''Tom tells her she looks beautiful whatever she's wearing.''