The image of an enraged bull charging a matador’s crimson cape is deeply fixed in popular culture, yet this spectacle is based on a biological misconception. The cultural belief that the color red incites fury in a bull is inaccurate. This enduring myth is primarily a product of the bullfighting arena, where a small red cloth is prominently featured. The animal’s biology prevents it from perceiving the color red the way humans do, meaning the hue of the fabric is irrelevant to its reaction.
The Truth About Bull Vision
Bulls, like most other cattle, possess dichromatic vision, meaning their eyes contain only two types of functional cone cells for detecting color. Humans have three types of cone cells, allowing us to see the full spectrum of red, green, and blue light. Bulls lack the red cone receptor, a condition similar to red-green color blindness in humans.
This limited color perception means that red does not register as a distinct shade to the animal. Instead, the red muleta—the small cape used in the final act of a bullfight—appears as a muted, dull yellowish-gray or simply another dark object. Bulls are sensitive to colors in the blue and yellow spectrums, but not those in the longer wavelength of red. Their visual world is dominated by these blue and yellow tones.
What Actually Provokes the Bull
The aggressive charge is not a reaction to color but an instinctual response to rapid, erratic movement. The matador’s actions, which involve whipping and waving the fabric, provoke the bull. This sudden motion triggers the animal’s natural fight or flight response.
The bulls used in bullfighting are bred for aggression and are placed in a high-stress environment designed to maximize their agitated state. By the time the matador introduces the cape, the bull is exhausted, confused, and filled with adrenaline from the preceding stages of the fight. The flapping of the cape serves as the most immediate target for its aggression. Experiments have demonstrated that a bull will charge at any color of cloth—blue, white, or green—if it is waved with the same speed and intensity as the red cape.
Why the Cape is Red Anyway
Since the bull’s vision renders the color red meaningless, the choice of a crimson cape is entirely for the human audience and the matador. The color red is highly visible to spectators, which enhances the visual drama of the performance. The theatrical nature of the fight is heightened by the perception of danger associated with the color.
The red color of the muleta also serves a practical purpose. The small cape is used during the final, bloody stages of the fight, where the bull is repeatedly injured. The deep red fabric helps mask the sight of the bull’s bloodstains from the audience, keeping the spectacle more aesthetically palatable. The color is retained due to centuries of tradition and its symbolic significance, rather than any biological effect on the animal.