Hilary Duff’s Colourist Just Spilled Her Formula For The Perfect Blonde Highlights

When Hollywood celebrities are looking to go blonde, or blonder, they make an appointment with seasoned colourist Nikki Lee. Working out of her recently-reopened L.A. hair salon, Nine Zero One, Lee's A-list roster includes the freshly-platinum Emma Roberts, The Real Housewives of Beverly Hills' Erica Jane, and most notably, her longtime client and close friend Hilary Duff.

For Duff's annual fall refresh, Lee gave the actress a boost with glossy blonde highlights. But she didn't just share a photo of the result; the celebrity colourist did us one better by spilling the exact formula and products she used to achieve our dream, post-vacation blonde.

According to Lee, Duff's brighter colour marks her upcoming return to set life. "Hilary's going to start filming Younger again soon," Lee tells us. "Once she’s on set, there will be a lot of heat styling, so we want her blonde to be protected."

As it pertains to Lee's step-by-step foiling formula, things gets a little technical (hair colour is chemistry, after all). For trained stylists out there, the process started with a full head of highlights, using Joico's Blonde Life Powder Lightener cocktailed with the brand's 20vol LumiShine Developer. Lee applied that mixture to the back and bottom sections of hair. Then, for the front and top strands, she traded the 20vol developer for the 30vol developer to achieve an even lighter blonde tone around the face.

Of course, given the harshness of bleach and foils on the hair, Lee had a treatment plan to counter potential damage. "The key to keeping Hilary's hair healthy while highlighting was not pulling any lightener through her ends," Lee explains of her pro tip. "The ends of her hair were already light, so instead of lightener, I added In Common’s Cashmere Fusion Cream to the ends while the highlights processed in the foils."

That's the gist of the perfect blonde: highlights, plus some extra TLC. So, if you're looking to take your hair lighter like Hilary this October, we'd recommend printing out Lee's secret-sauce for your own colourist and chatting through the best treatment plan for your hair colour and texture. It's the next best thing to scoring a spot on Lee's wait list.