The widespread belief that bulls are enraged by the color red is one of the most enduring myths in popular culture, often reinforced by the dramatic imagery of bullfighting. Scientific understanding of bovine biology demonstrates that a bull’s reaction is entirely independent of the color red. The animal’s response is a purely behavioral reaction to movement and provocation, not a chromatic aversion.
The Biological Reality of Bovine Vision
Cattle, including bulls, are dichromats, meaning their visual system relies on only two types of cone photoreceptor cells in the retina, unlike the three found in most humans. One cone type is sensitive to shorter wavelengths, peaking around the blue-violet spectrum, while the other is sensitive to medium-to-longer wavelengths, peaking in the green-yellow region. The complete absence of a separate cone mechanism sensitive to the red spectrum means bulls are unable to perceive red as a distinct color, effectively making them colorblind to it. The world appears to a bull in shades of blue, yellow, and gray. Consequently, the color red is not seen as a bright, infuriating hue but rather as a dull, indistinct shade, likely a dark gray or brown, indistinguishable from various other colors in the arena.
The True Stimulus: Movement and Agitation
Since the bull does not register the color red, its aggressive charge is a reaction to the rapid, sweeping motion of the cloth and the behavior of the matador. Bulls are highly sensitive to movement, and any sudden, erratic action within their field of vision serves as a trigger for a defensive or aggressive response. The matador uses the large magenta and gold capote cape in the initial stages of the fight, and the bull reacts to this large, flapping garment with the same intensity as it does to the smaller, red muleta used later on. The bull’s charge is a predictable behavior directed at the most threatening and quickly moving object, which is the waving cape, not the stationary matador. Studies have confirmed this behavioral response, showing that bulls will consistently charge any object—regardless of color—if it is moving quickly, while ignoring a person standing still, even if that person is wearing red.
Why Bullfighting Capes Are Red
If the color red is invisible to the bull, the continued use of the red muleta cape in the final stage of the bullfight is entirely for the human audience. The choice of red is a matter of tradition and spectacle, rooted in centuries of cultural practice, adding a psychological element of passion and dramatic flair for the spectators. Crucially, the red color serves a highly practical function in the final moments of the event. The deep red hue is effective at concealing the animal’s blood, which is dark and would otherwise stain a lighter cape. By masking the bloodstains, the red cloth helps maintain the visual drama of the performance and reduces visual distress for the audience.