Credit: INF Photo; Jeffrey Mayer/WireImage

Emma Stone debuted fresh blond hair over the weekend, a drastic color change from her deep red roots. But this kind of intense transformation, which she did to prepare for her role in the new Spiderman movie, didn’t happen with just a box of dye and a few hours to kill. In fact, it took 13 hours over three days and two colorists—Tracey Cunningham of Beverly Hills' Byron & Tracey Salon and Marie Robinson, who runs her own salon in New Yorkto create Stone’s golden look. “She has pale pink undertones to her skin, so it was important to find a balance of pale blond with just the right amount of gold and strawberry,” Robinson told InStyle exclusively. “It was tricky because we needed it to be a believable color for Spiderman's fans and work for her everyday life.” So, why was the process so intense? As Cunningham explained: “It takes a long time to do it carefully!”