why are bulls enraged by the colour red? Truth be told, they are not. It is a common misconception about cattle (particularly bulls) that the colour red provokes them. Cattle are red-green colour blind. The myth arose from the use of red capes in bull fighting. However, bulls do have two kinds of colour receptors in their retinas and can, theoretically, distinguish some colours. It is not the colour of the cape that angers the bull, but the movement of the fabric that irritates and incites it to charge.