Colour blindness breakdown

Overview

“Color Blindness is not ‘Color Blindness’. There are still a lot of people who think that if you are colorblind you really can’t see any colors. But the term is misleading, as more than 99% of all colorblind people can see colors. A better wording would be color vision deficiency, which describes this visual disorder more precisely.”

— Daniel, Colblindor, Color Blind Essentials ebook

The human eye perceives colour by a mixture of three different cones that are sensitive to specific wavelengths of light: red, green and blue.

A colour deficiency is when your sensitivity to a cone is shifted, perceiving a narrower colour spectrum.

Some statistics

Generally, colour blindness is a genetic condition affecting approximately 1 in 12 men (8%) and 1 in 200 women (0.53%) worldwide. This means:

In Britain, there are around 3 million colour blind people — about 4.5% of the entire population
Around 300 million people worldwide are affected, roughly equivalent to the total population of the USA

Types of colour blindness

Dichromacy

Only two different cone types can be perceived. The third is missing completely.

Spectrum	Denomination	Prevalence: Male	Prevalence: Female
Red blind	Protanopia	1.01%	0.02%
Green blind	Deuteranopia	1.27%	0.01%
Blue blind	Tritanopia	0.0001%	—

Anomalous trichromacy

All three cone types are present but with reduced sensitivity in one cone, resulting in a narrower colour spectrum.

Spectrum	Denomination	Prevalence: Male	Prevalence: Female
Red weak	Protanomaly	1.08%	0.03%
Green weak	Deuteranomaly	4.63%	0.36%
Blue weak	Tritanomaly	0.0002%	—

Monochromacy

Either no cones can be perceived, or just one.

Spectrum	Denomination	Prevalence: Male	Prevalence: Female
Greyscale	Achromatopsia	0.00003%	—

Facts about red-green colour blindness

Red-green colour blindness is a generic term covering several spectrums: red blind, red weak, green blind, green weak
More than 99% of all colour blind people experience a form of red-green colour vision deficiency
Severity varies — from slightly reduced, through moderate, to strong or complete absence of a colour cone
The whole colour vision system can be affected, not just specific hues