Matt Rez is a hair colorist for people whose hair color is highly visible and maybe even consequential, as far as these things go. But you’d never know it. In fact, you probably haven’t heard of him. And that might be by design.

Rez has painted, foiled, and streaked Kendall Jenner, Kaia Gerber, Hailey Bieber, Adele, Chrissy Teigen, Margot Robbie, and you-name-it more. He’s the most known unknown image-maker around.

It would be hard to find someone less likely to rise to the top of the beauty-service business. Rez was born and raised in Tehran. “It was the Iran-Iraq War, bombs were going off constantly, my parents were taken away all the time. It was constant chaos.” Rez’s aunt was imprisoned in Tehran throughout his childhood. “We would visit her once a week. The [police] would say, They’re going to execute her today. Come say good-bye. We’d go. We’d wait. They put all the women prisoners in front of a firing squad—blindfolded—and start shooting blanks. She made it out after 10 years, but we lived in a constant state of fear.”

It would be hard to find someone less likely to rise to the top of the beauty-service business.

Today, Rez works out of a small studio in a place called Salon Republic—a collection of beauty workspaces in a glossy building on Wilshire Boulevard. Blowouts, trims, highlights, manicures—it’s like a tiny, high-end office park for the polishing of surfaces. A place where the well-dressed women of West Los Angeles swish in and out of fragrant, mirror-lined rooms. It’s about as far from the firing squads of the Islamic Republic of Iran as one can imagine.

Rez left Iran at nine and eventually settled with his family in Wisconsin. For a gay, Iranian boy, uprooted and planted in the Midwest, adolescence wasn’t easy. Rez was in middle school when “September 11 happened, and everybody just hated us. I stopped going to school,” he says.

He wanted to change his neighbors’ opinions, so he got to work. “I was always enamored by Halloween—we never had anything like that in Iran. I made a haunted house inside our garage and charged people five bucks. I raised about a thousand bucks for the Firefighters Fund of New York. And the [local] news got wind of it and interviewed me. I wanted to show people that I wasn’t a terrorist.”

Left, awe-inspiring auburn highlights; right, pure platinum on an actress whose last name rhymes with “hue.”

Those formative years led him, circuitously, to his future career. “I went to school with mostly Caucasian kids—they would come back from summer break with beautiful, blond highlights. And there I was with my dark, curly, coarse hair, and I’d look at them, and I was like, I want that,” says Rez, jabbing his finger in the air, presumably pointing to the invisible kids from seventh grade. So Rez did what any future colorist would do. “I bought a bleaching kit—one with a perfect, beautiful white boy on the cover. I ended up looking like an orangutan.”

Rez fixed the orange and eventually “convinced the girls at school to let me do their hair on the weekends. They were like, ‘Do you know what you’re doing?’ I’m like, ‘Of course!’” Rez bought bleach and boxes of hair color, mixing and making it up as he went along.

It didn’t go particularly well. When he turned his cousin’s hair every shade of crazy—gray, orange, white, red, brown, you name it—she had to go to a salon to have it fixed. “I watched a woman take something heinous and make it passable,” he says. From that moment on, “I knew I wanted to do this forever.”

Those who know Rez admire his skill at natural-looking color that doesn’t wreck the hair, something he learned by experimenting on himself. “If you do highlights, either there are too many and it destroys the hair, or it’s stripy.” He figured out a way to connect the base color with the highlights: “It gives the illusion of a lighter base without lightening your base.”

Rez’s first job was at a small salon in Sherman Oaks, a suburban pocket in the San Fernando Valley. As lovely as it is, Sherman Oaks isn’t a hotbed of hair trends. Rez decided to “bite the bullet and go over the hill.” He was offered a chair at the Ramirez Tran Salon, in Beverly Hills, as long as he filled it with clients. “I had three months. So I hustled,” he says. “Instagram had just become a thing. And I saw this girl—Chiara Ferragni.” Rez reached out to the since disgraced Italian influencer and offered to do her hair whenever she was in L.A., gratis. She had two million followers on Instagram at the time. “Within 30 minutes, I got an e-mail back.” For the next six months, Rez gave her weekly blowouts but never did her color.

With influencers comes influence. Soon Eiza González, the Mexican actress, was getting highlights. Then a friend sent Margot Robbie his way. In a flash, the word spread that there was a new colorist in town.

Rez moved to the Mèche Salon in Beverly Hills, a hub of some of the leading experts in the business, starting with its owners: Tracey Cunningham, a colorist, and Neil Weisberg, a hairstylist. After years under their tutelage, he set out on his own. Even though his current salon has just one chair, its reach is sizable.

“I used to dream about seeing my work in the Sherman Oaks Patch,” Rez says. Now he’ll pass a billboard on Sunset or catch a movie trailer, and there’s Penélope Cruz, swinging her caramel-and-brown hair; Natalie Portman, a shiny, light-streaked brunette. There’s no signature identifying Rez’s work, and his name doesn’t appear in the credits. But that’s O.K. He knows exactly what he’s doing.

Danielle Pergament is a Los Angeles–based writer. Formerly an editor at Goop, she frequently contributes to The New York Times