Question: Do you know why some people are colourblind?

Hussain Jaffery answered on 16 Nov 2015:

In the UK alone, about 4.5% of people are colourblind – mostly males. This means they can only see certain colours, not necessarily no colours.

Colourblindness occurs when a person lacks correct function of all of the colour receptor cone cells in the eye. There are three major colour receptor cones cells: blue, green and red (the combination of these three primary colours makes up every other colour. If you only have one or two of the receptors, you can only see the colours that make up the combinations of the receptors you have.

The colourblindness affects men mostly because the genes for the photoreceptors are located on the X chromosome, which men only have one copy of, while women have a backup copy, having two X chromosomes.