I noticed a story today about a bull that escaped during a rugby game in France. Why would a bull even be there? I have no idea. But what interested me was the trope that was repeated in the article about the concern that one of the teams was wearing red shirts and that this could put those players in particular danger.

As you may know, bull fighters use a red cape during bull fighting events and this is popularly believed to be to enrage the bull.

However, it turns out that bulls are dichromats. They only have two types of cones – the light-sensitive cells in our eyes – and they are missing the long-wavelength cones. This makes them colour blind and red-green colour blind in particular.

It isn’t the case that bulls are enraged by red; it is the movement of the cape that irritates them. It is my understanding that the red colour is used so that the cape doesn’t show the blood. This was discussed in the first of my podcasts – do dogs see colour – which you can listen to here.