In the most common form of colour blindness, people have difficulty distinguishing red from green. Our colour blind ancestors may have found it tough to recognise when someone was blushing, for instance, or they may have had trouble choosing a ripe fruit or spotting snakes with colourful warning marks.
Similarly, a South American primate might have difficulty identifying social signals such as the bright red head that indicates fitness in the bald-headed Uakari. They may find it tough to identify ripe food or colourful threats such as an orange-furred ocelot or jaguar up against a green forest background.
Benefits Of Blindness
But colour blind vision might actually be an advantage in some situations. After all, colour signals can be overwhelming, leading us to pay more attention to colours than patterns. Predators can exploit this by using camouflage to ambush their prey, so the ability to spot a threat is significant.