“Bulls are attracted to or agitated by the color red.”

The presence and intensity of red coloration correlate with male dominance and testosterone in a variety of animal species, and even artificial red stimuli can influence dominance interactions. In humans, red stimuli are perceived as more threatening and dominant than other colours... Colour had a significant effect on how often a stimulus was categorized as ‘angry’... Red therefore appears to carry specific biological signals in both humans and other animals.

Experiments have suggested that cattle can only discriminate long wavelengths of light (colored red) from short (blue) or medium (green) wavelengths, and not short from medium wavelengths; however, stimuli were inadequately balanced for intensity. In this study, an initial group of calves was trained to discriminate between three isoluminant sources.

Surprisingly, bulls don't actually hate red; they are essentially color blind to it. Instead, their reactions stem from movement rather than hue. Bulls possess dichromatic vision—meaning they have two types of cone cells in their eyes—allowing them to see blues and yellows while rendering reds nearly invisible. To a bull, that bright crimson looks more like a dull brownish-gray or yellowish shade.

Bulls, along with all other cattle, are color-blind to red. Thus, the bull is likely irritated not by the muleta's color, but by the cape's movement as the matador whips it around. In support of this is the fact that a bull charges the matador's other cape — the larger capote — with equal fury. Yet this cape is magenta on one side and gold or blue on the other.

The idiom "red rag to a bull" means to aggravate someone, make them angry, or incite violence. However, the claim that the color red triggers bulls, which is why they charge at a matador's red flag (muleta) in a bullfight, is widely debunked. Bulls are colorblind.

Red does not make bulls angry. Science shows they react to movement, not colour... Controlled experiments confirm these findings. Bulls react identically to moving objects of different colours. Red, blue or white produce similar responses. When objects remain still, bulls remain calm.

“Bulls, along with all other cattle, are color-blind to red,” writes Brooke Borel of LiveScience.com. “Thus, the bull is likely irritated not by the muleta’s color, but by the cape’s movement as the matador whips it around. [...] To prove it once and for all, the guys from Mythbusters [...] put three matadors in a ring, each holding different colored flags (red, white and blue). “The red, blue and white flags got equal, half-hearted attacks when they were motionless,” they reported. “In order to elicit an aggressive charge response from the bull, the flags had to be waved.”

Cows can distinguish red from green or blue but have difficulty distinguishing between green and blue (Phillips and Lomas, 2001, JDS 84:807-813). If you looked at the world through “cow-coloured” glasses you'd still be able to see colour, but perhaps not with the intensity that we can. Cow eyes can register wavelengths of around 450 nm and 550 nm (Jacobs et al 1998 Vis Neuro Sci 15:581-584).

The simple, scientific truth is that bulls, like most other bovines, are dichromats. This means they only have two types of color-detecting cone cells in their eyes, whereas humans have three. The colors they can see are limited to a range of blues and yellows. They simply cannot perceive the color red at all.

The long-held belief that the color red makes bulls angry is unquestionably false. Science has shown that bulls are color blind to red, and controlled experiments have proven that movement is the true trigger for charge. This myth is perpetuated by a powerful combination of cultural tradition and human psychology.

Bulls don't get agitated by the color red. In fact, there is very little evidence for any color aggravating bulls into causing damage. Bulls, like other ungulates (animals with hooves), have dichromatic vision. They have two different cone cells, those cells in the retina that detect color.

Do bulls hate the color red? The answer is no. Surprisingly, bulls are colorblind to red. The true reason bulls get irritated in a bullfight is because of the movements of the muleta. Bulls, including other cattle, are dichromat, which means they can only perceive two color pigments.

Cattle, including bulls, have dichromatic vision with two cone types sensitive to short (blue) and medium (green-yellow) wavelengths, but lacking functional long-wavelength (red) cones, similar to red-green color blindness in humans. This is established in veterinary ophthalmology; bulls respond aggressively to motion as a predator avoidance instinct, not color, confirmed by behavioral studies since the 1970s.

{ts:1605} they seem to go towards movement rather than actually for the color red [...] it's a common misconception that they are color blind but in fact they're not [...] they're what's called di chromates they can see two main color types [...] Bulls can see red but there is no scientific evidence to prove that makes them any more enraged than any other color absolutely there is no

A bull's vision is very similar to that of a human with red blindness (known as protanopia). To them, a red cape looks yellow on gray. It is the threatening, waving motion of the matador's red cape that enrages a bull, not the color. Taken from: "Scientific questions with surprising answers", which was answered by Dr. Christopher S. Baird – Professor of Physics at West Texas.

{ts:7} since those capes are always red most people tend to think that it is the red color that makes bulls angry and provokes them to attack but actually along with all other cattle bulls are color blind to red {ts:19} it's the movement of the cape that irritates them or in other ways incentivizes them to chase after it