rita hazan
Credit: Frank Trapper/Corbis; Ciao Hollywood/Splash News; Frank Trapper/Corbis

What's the secret to Hollywood's best hair color? Perhaps the question is really who. Meet Rita Hazan, a New York-based colorist responsible for tons of celebrity strands. For our March issue, Hazan dished on her top clients:

1. Jennifer Lopez's sunny highlights: "When I started working with Jennifer in the '90s, I thought it would be fun to experiment with honey highlights. I had no idea it would become such a big part of her look," the colorist says. Now Lopez gets "inside highlights" that show when she flips her hair.

2. Rachel Weisz's bold espresso: Hazan gives Weisz a cool brown to avoid brassiness. "If it starts looking too inky, I'll break it up with subtle highlights," she says.

3. Jessica Simpson's buttery blond: "The first time Jessica came to see me [at age 18] was to fix a bleached-out platinum dye-job," says Hazan. Now Simpson receives a base of golden blond with paler blond highlights.