A common misconception about cattle (particularly bulls) is that they are enraged by the color red (something provocative is often said to be "like a red rag to a bull"). This is incorrect, as cattle are red-green colour-blind.
The myth arose from the use of red capes in the sport of bullfighting; in fact, two different capes are used. The capote is a large, flowing cape that is magenta and yellow. The more famous muleta is the smaller, red cape, used exclusively for the final, fatal segment of the fight. It is not the color of the cape that angers the bull, but rather the movement of the fabric that irritates the bull and incites it to charge.
Although cattle cannot distinguish red from green, they do have two kinds of colour receptors in their retinas (cone cells) and so are theoretically able to distinguish some colours, probably in a similar way to other red-green colour-blind or dichromatic mammals (such as dogs, cats, horses and up to ten percent of male humans).
https://en.wikipedia.org/wiki/Cattle
[Added reference link - McG]