What does it mean when someone is colour blind?

By Sophia Miettinen

Colour vision deficiency, more commonly known as colour blindness, is a condition where people struggle to recognize and tell the difference between certain colours. People who are colour blind are normally born with it, and it is not as uncommon as you may think! Around 1 in 12 boys and 1 in 200 girls have red-green colour blindness, which is the most common type of colour blindness.

There are many different types of colour blindness. Normally when you are colour blind, it does not mean you can’t see any colour at all, but colours may look dull and very similar, especially in dim light. If you have red-green colour blindness, you might struggle to tell the difference between any colours made up of red and green, so colours such as red, orange, yellow, brown and green can all appear very similar. This can make looking at traffic lights very confusing! Other types of colour blindness make it more difficult for you to tell the difference between colours made of blue and yellow, and very rarely you may not be able to see any colours at all and everything appears to be grey.

Why does colour blindness happen?

Colour blindness is usually genetic, which means that it is passed down to you from your parents. In the back of your eyes, which is called the retina, you have special cells that allow you to see light. There are two different types of cells that allow you to see light, and these cells are called rod and cone cells. Rod cells allow you to see when it is dark, and cone cells allow you to see colour when it is light. There are three different types of cone cells; each one can detect either red (R), green (G) or blue (B) best, as you can see in the picture. All three of the different types of cone cells have special sensors in them made up of something called an opsin that allows them to be able to detect certain colours.

Your body is made up of lots of genes that each contain information called DNA. This DNA contains instructions for all the cells in your body to function, but sometimes the DNA is not working properly. If the genes that your parents gave you cannot make opsins properly, then one or more of your cone cells won’t be able to detect their colour best. This means the other two cones will need to try to detect that colour instead. For example, if your red cone cells don’t work, the green cone cells will try and detect red This means the red will look more like green to a colour blind person than red would usually look.

There is no treatment for colour blindness, but as colour blindness is usually mild, your daily life won’t usually be affected and you may not even know you have it!

If you can see red, blue and green light equally, your vision is called trichromatic. Scientists are now discovering that some people are tetrachromatic, meaning they have an extra cone cell type, and by having four cone cell types it means that some people may have superhuman vision and are able to see more than ten times as many colours than most of us!