ABC News' Linsey Davis and Daisha Riley report:

Brad Pitt, Jennifer Aniston and Jennifer Lopez have gone from blonde to brunette over the years. But now, the salon that claims it has styled the locks of such celebrities in the past is seeing red.

John Sahag Ltd., a New York hair salon to the stars, has taken one of its former stylists to Manhattan Supreme Court. The company claims that when stylist Reyna Garcia left to work for a competitor in June, she took top-secret, hair-color formula cards.

"Some stylists or colorists do not want to reveal what their hair colors are because of the fear of replicating," Nikki Ferrara, the color director at Sally Hershberger Salon in New York City, told ABC News.

"It's science, art, cooking," said Ferrara, who has no connection to the case. "It is one big, complex formula."

The court documents refer to the color-formula cards as "the key to the business," and "the road map that came into existence after consultation with the customer."

The 5-by-7 cards list the customers' names, addresses, telephone numbers, dates they visited and precise color formulas, information Sahag Ltd. considers a trade secret.

The suit alleges that four Sahag clients have told them that Metodo Rossano Ferretti New York, where Garcia now works, called them to say their appointment had been changed and that they should now go to Ferretti for their hair-coloring.

The court Tuesday reportedly barred Garcia from using the formulas, but allowed Ferretti to contact her former clients.

Garcia, Ferretti and John Sahag Ltd. declined comment to ABC News, but attorneys for Sahag have maintained it was unlikely Garcia could have committed this information to memory because the cards contained codes with complicated formulas signifying different mixtures, number of applications, levels and tonal direction and even how much shimmer or gloss was needed for the hair.

Ferretti lawyer Steven Miller said his client has no cards from Sahag, and accused Ferretti of going on "a fishing expedition" to find out which customers have switched salons, according to the Daily News.