“Bulls are enraged by the color red.”

It's a widely held belief that the color red sends bulls into a furious rage, a misconception deeply rooted in the dramatic spectacle of bullfighting. The iconic image of a matador waving a vibrant red cape, or muleta, as a bull charges forward has led many to assume that the crimson hue is the direct cause of the animal's aggression. This powerful visual, combined with human psychological associations of red with anger and danger, has cemented the myth in popular culture and common idioms.

However, scientific evidence busts this long-standing myth. Bulls, like most cattle, are largely colorblind to red. Their vision is dichromatic, meaning they primarily perceive colors in the blue and yellow spectrums. To a bull, the matador's bright red cape likely appears as a dull yellowish-gray or brownish-gray. Numerous studies, including experiments by the Discovery Channel's "MythBusters," have demonstrated that bulls react to the rapid, erratic movement of the cape, not its color. When presented with stationary flags of various colors, including red, bulls showed no preferential aggression. Their charge is an instinctual response to perceived threats and movement in their environment.

The enduring use of red in bullfighting capes, therefore, serves purposes unrelated to the bull's vision. Historically, the red color was chosen for aesthetic reasons, adding to the visual drama and excitement for the human audience. More practically, the dark color helps to mask bloodstains that may occur during the later stages of a bullfight, making the spectacle less gruesome for spectators. So, while the phrase "like a red rag to a bull" remains common, the truth is that it's the agitated flapping, not the specific shade, that truly catches a bull's attention.