Why Mary-Kate Olsen Went from Blonde to Brunette

Mary-Kate Olsen on June 4, 2012 in New York City. Dimitrios Kambouris/WireImage

Mary-Kate Olsen turned heads this week when she stepped out rocking a new glossy brown hair color.

But for those speculating that she underwent the change solely for her new 17-years-her-senior beau, Olivier Sarkozy, her hair pro tells Us Weekly otherwise.

"She was simply ready for a change," Harry Josh, John Frieda International Creative Consultant, explains to Us. "She always mixes it up, and she wanted to do it before the CFDA [Awards]." (Olsen, alongside her fraternal twin Ashley, debuted her new shade at the annual fashion event in NYC on Monday. The sisters took home the Womenswear Designer of the Year Award for their line, The Row.)

For those who are itching to go darker like the 25-year-old fashion designer, Josh says the transformation can be foolproof — and done right at home!

"It's fun to experiment with a new hair color and deep, rich brunette shades tend to leave hair looking healthy and shiny," he tells Us. "It's difficult to recommend at-home hair color to replicate a professional color job at-home, but John Frieda's Precision Foam Hair Color in 4BG ($12.99, drugstore.com) delivers professional results. Plus, this dark, chocolate brown shade is incredibly gorgeous!"

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