Late-night discussion about the colour vision of dogs, shrimp, bees, cows, bulls and many more. Do dogs see in colour? Are bulls really enraged by the colour red? Does colour even exist?
Dogs are dichromats; that means they have two types of light-sensitive cells (cones) in their eye. Most humans are trichromats. We don't really know what it's like for a dog - or any other species - to experience colour. However, we can compare their physiology with ours and we can conduct behavioural experiments. If a dog, for example, can be trained to discriminate between two colours then it tells us something about their colour vision. In fact, most mammals are dichromats including cats and bulls. Bulls have poor colour vision in the red part of the spectrum; it's more likely that the motion of the cape - rather than its colour - attracts their attention.