When Laurie, the heartthrob-next-door of Louisa May Alcott's 1868 novel Little Women, is shown boy and girl twins, he asks, "Which is which?"
"Amy put a blue ribbon on the boy and a pink on the girl," Jo replies. "French fashion, so you can always tell."
According to Jo B. Paoletti, author of Pink and Blue: Telling the Girls From the Boys in America, "blue for boys, pink for girls" may have been common practice in 18th century France, but in United States, the color rulebook had yet to be written.
Back in the day, infants of all genders wore white frocks—white, because it could be bleached of any infant spewage, and frocks, because it's easier to wriggle a baby into a dress than into britches. Franklin Delano Roosevelt's 1884 toddler photo depicts our dignified to-be president sitting primly in a white skirt and patent leather shoes.
Eventually, parents began dressing their infants in "the colors of springtime," but it wasn't until World War I that those colors became gender signifiers. In June 1918, the Earshaw Infants' Department instructed parents, "The generally accepted rule is pink for the boys, and blue for the girls. The reason is that pink, being a more decided and stronger color, is more suitable for the boy, while blue, which is more delicate and dainty, is prettier for the girl."
But not all manufacturers agreed. In 1927, Time magazine printed a chart showing which sex-appropriate colors were approved by major department stores (Filene's and Marshall Fields advocated pink for boys; Macy's said pink was for girls).
Though the decision could have gone either way, by 1940 most advertisers agreed on pink for girls, blue for boys, and in post-World War II consumer culture, gendered clothing and colors were all the rage.
Despite its highly contested beginning as the color of girlhood, pink has remained steadfast in its symbolism. Remember when "America's toughest sheriff" Joe Arpaio fitted male inmates at an Arizona prison with pink undies to "reduce underwear theft?" Earlier this year, the 9th U.S. Circuit Court of Appeals ruled that the mandatory pink undergarments were a form of "punishment without legal justification," noting that the selection of pink was meant to symbolize the loss of prisoners' masculinity.
While metrosexual fashion reclaims pink as a "manly" hue, I'm not so sure if pink and blue will ever lose their cultural significance (plus, sporting a shirt that reads, "Real Men Wear Pink" only reinforces the line the between masculine/feminine gender roles). But the history of pink and blue shows us just how arbitrary gender signifiers can be, and in the genderpocalypse, that's knowledge we can apply to just about everything else.