When we were trying to understand more about colour vision today, some people asked some really good questions about how people who are ‘colour blind’ see colours. This is very difficult to describe exactly as it is difficult to know exactly what someone sees compared to somebody else. However, this image may give you some idea of the effect that being ‘red-green’ colour-blind has on how somebody sees the spectrum of colours we looked at today. Looking at this image, you can see why, for some people, blues would become such an important colour.