What Colours Do You See?
Well, the words "affected" and "condition" sound inaccurate for someone that can see a full rainbow of different shades where most of us can see one or two nuances.
It is due to a gene that influences the development of the retina. Almost everyone has three types of “cone cells” in their retina. Each of them responds to a different bandwidth of light. Although the exact sensitivity may vary between people, overall one person’s colours should roughly match another person’s. The exceptions were thought to be colour-blind people, where one of the cones is faulty.
In the opposite case, an extra cone would offer a hundred different variants to each colour that humans normally see. We know that this happens in nature: zebra finches and goldfish both have a fourth cone that seems to help them differentiate apparently identical colours. They have a kind of super-vision, like people with tetrachromacy.
One of these people is the Australian artist Concetta Antico, a painter that is able through the use of the palette to let us peep from the window of her perception of surrounding colours. The picture shows one of her works.