Lauren, who rose to fame in Laguna Beach: The Real OC before starring in The Hills, decided to take the plunge after experimenting with wash-in wash-out colour.
The US star's new purple hue will last up to eight weeks and she admits she did it after admiring fellow celebrities with similar coloured hair.
Could she mean Kelly Osbourne and Nicole Richie?
Lauren revealed her new 'do on her website Laurenconrad.com in a post titled 'Pretty In Purple'.
The fashion designer said: "As I've mentioned before, I keep temporary pink hair dye in my shower for whenever I'm in the mood for a fun beauty look.
"But this time, I decided to take the plunge and try a semi-permanent colour.
"I really didn't think that purple was my colour, but after seeing several others wear it recently, I decided to give it a try."
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