“Bulls are enraged by the color red.”

The enduring image of an enraged bull charging at a matador's vibrant red cape is deeply ingrained in popular culture, leading many to believe that the color itself is the catalyst for the animal's fury (Review). This widespread misconception primarily stems from the dramatic spectacle of bullfighting, where the crimson muleta is a central and visually striking element. The theatrical nature of the sport, with the matador seemingly provoking the bull with the red cloth, has historically fueled the idea that red is a universally irritating color for these powerful animals.

However, scientific evidence thoroughly debunks this myth. Bulls are, in fact, colorblind to red and green, possessing dichromatic vision similar to humans with red-green colorblindness. This means they perceive red as a shade of yellowish-gray or blue, rather than the vivid hue we see. Their aggressive reaction during a bullfight is not triggered by the color of the cape, but by its rapid, erratic movement. Studies, including experiments that have used capes of various colors, confirm that bulls charge at any moving object, regardless of its shade, as it is the motion that stimulates their instinct to react to a perceived threat.

The tradition of using a red cape persists for reasons entirely unrelated to the bull's vision. The color red adds to the dramatic flair of the bullfight, creating a more intense and captivating experience for the human audience. Crucially, the red fabric also serves a practical purpose: it effectively masks the bloodstains that may occur during the later stages of the bullfight, making the spectacle less graphic for spectators. Thus, the long-held belief that bulls "see red" is a classic example of human interpretation overriding biological reality, perpetuated by centuries of tradition and visual storytelling.