Long before Friends fans flocked to salons asking for Jennifer Aniston’s “The Rachel,” Jean Harlow popularized another head-turning hairstyle: locks so blonde they looked white. Her appearances in films like Hell’s Angels (1930) and the aptly titled Platinum Blonde (1931) inspired women to bleach their hair, too.

Hairdressers used hydrogen and ammonia to turn tresses pale yellow, but the secret to achieving that silvery shimmer was a blue chemical solution called a “blue rinse.” It wasn’t an outrageous idea, since people were already accustomed to brightening their white linens with bluing agents. Almost immediately, beauticians and advice columnists started recommending blue rinses to older women as a way to restore luster to their gray or yellowish-white hair. Though it worked well when properly done, a botched rinse could leave hair looking anywhere from slightly bluish to decisively purple. This happened frequently—and not always by accident.

“Some women, having observed the lavender effect and decided that it heightens rather than lowers their standing in the beauty scale, go in for it deliberately,” a columnist wrote in The Baltimore Sun in 1939. “At this particular moment, it appears, the ladies are on the verge of forgetting the original intention of the blue rinse and are using it for its own sake.”

Jean Harlow getting her hair set in 1933.Keystone/Getty Images

The colorful craze might have lost steam if Hollywood had soured on platinum hair, but Harlow was far from the last of the blonde bombshells. Marilyn Monroe helped usher the fad right into the 1960s, with more than a little help from Clairol’s “Blondes have more fun” advertisements. Blue rinses persevered, and blue hair continued to be marketed to older women as a technique for graceful aging.

“If you have gray hair and like it, why not dramatize it a bit? Use a blue rinse,” Edyth Thornton McLeod wrote in a 1953 article for her syndicated column Beauty After Forty. “You can have a soft blue cloud effect or you can make it deep and dramatic and match your accessories to the color.”

By the 1970s, the phrase blue-rinse brigade began popping up in reference to old ladies doing just about anything, from attending Scottish National Orchestra concerts to protecting the streets of Vienna, Austria, from petty criminals. It also became a popular (and occasionally pejorative way) to describe the older female voters who furthered the Conservative agenda in Britain.

Margaret Thatcher with an unofficial member of the blue-rinse brigade in 1977.Frank Barratt/Getty Images

While blue hair might not be quite as popular among older women as it was a few decades ago, the fad hasn’t died out. Jean Harlow’s blue baton has been passed to Lady Gaga, multiple Kardashian sisters, and also Benjamin Netanyahu.