Colour blindness is a slight misnomer and should more accurately be defined as Colour Vision Deficiency (CVD).

This is a condition where some people find it difficult to distinguish between different colours under normal lighting conditions. They can normally perceive, or understand, almost every colour in the spectrum but 'shades' of colours can be problematic.

It is usually a genetic or hereditary condition present at birth, although sometimes acquired through ageing, injury to the eye and side effects of some medication. Eye problems like glaucoma (build up of pressure in the eye), cataracts (clouding of the eye lens) or diabetic retinopathy (high blood sugar damaging the back of the eye (retina) can also contribute to the condition.

Colour blindness affects 1 in 12 men and 1 in 200 women in the world. In Britain 4.5% of people are colour blind. The condition is normally classified as a mild disability but it can affect the future career choices of an individual. 

Image of two sets of traffic lights. The set on the right is simulated protanopia.

Driving a motor vehicle for instance; some countries in Europe (Romania) and Asia (India) won't allow those with any type of colour blindness to hold a driving licence, particularly for commercial driving. Most people who are red/green colour blind cannot tell the difference between red (stop) and green (go) traffic lights (Fig.1). A person may only be able to tell red and green traffic lights from the position of the lights that are lit - red (stop) is always on the top.

Normal vision is generally essential to becoming a pilot, but depending on the severity of the condition, a mildly colour blind person may still be able to fly following certain tests.

Electricians may have a problem because the electronic wiring, transformers, resistors and capacitors are colour-coded, using black, brown, red, orange, green, yellow, blue, white, silver, violet, grey, white and gold.(Fig.2)

Fire fighters need to be able to identify the variety of colour coded fire safety equipment. 

Computer cabling - the image at the bottom is simulated protanopia.

Police officer, essential to have normal vision particularly when someone has to describe an individual and what they were wearing, a bit difficult if they cannot define red or brown.

Hairdressers may have difficulties colouring a customer’s hair. Baggage handlers, since some airlines use colour coded tags for bags to indicate its contents. 

The majority of colour blind people are, so-called, anomalous colour blind. That is to say they see colours in a more restricted way compared to colour normal i.e. many colours which look quite distinct to colour normal look quite similar for an anomalous observer.  A minority of people with CVD are pure colour blind in that they lack of particular colour sensitive cells  (cones) in the back of the eye. Pure colour blind people have a much more severely impaired view of the colour world. There are a third class of colour blind people who lack two (or possibly all) cone sensors. Their vision is mediated by a single cone class or for rod (low-light sensitive sensors) only. However, there are only a small number of people who are truly colour blind and see in monochromatic vision. 


[1] Colour Blind Awareness. Extensive website on Colour Blindness. Accessed:February 2016.

[2] Colbinder. All about colour blindness. Accessed: March 2016

[3] COBLIS. Colour blindness simulator. Accessed: March 2016

[4] Wikipedia. Color Blindness. Accessed: March 2016. Content: 7.2 Occupations.

[5] Color Matters. Color plays and important role in the world we live in. Accessed: April 2016

[6] Rogers, A. (February 2016) Wired Science. A Year Ago, the dress murdered the idea of objective color. Accessed: April 2016.

[7] Wong, B. (2011) Color Blindness. Nature Methods, Vol.8 No.6, 441. 

[8] What do you really know about colour blindness? (2015) British Journal of School Nursing. Vol.10 No.4, 197-199

[9] Santini, B. (June 2015) The Science behind Color Enhancement. 20/20 Features Magazine, 39-46

[10] Color Blind Essentials. eBook by Daniel at Accessed: March 2016

[11] Dalton, J. (1794) Extraordinary Facts relating to the Vision of Colours with observations.

[12] Ishihara, S. The Series of Plates Designed as a Test for Colour-Deficiency. 38 Plate Edition.

[13] Hasrod N, Rubin A. (2015) Colour vision: A review of the Cambridge Colour Test and other testing methods. Afr Vision Eye Health. 74(1),Art.#23,7 pages.

[14] National Eye Insitute. Facts about Color Blindness. Accessed: April 2016.

[15] Quora. Can I get a driving licence in the UK and US if I am color blind? Accessed: June 2016.

[16] Quora: How can I get a driving licence in Delhi if I was rejected in the colour blindness test? Accessed: June 2016.

[17 ]Quora: Will RFID luggage tags mean no more lost luggage? Accessed: June 2016

[18] Tetrachromacy Project. Institute of Neuroscience at Newcastle University. 

[19] Holba, A. Lukacs, B. CRIP RMKI, H-152 Bp. 114 Pf. 49, Budapest, Hungary. On Tetrachromacy. Accessed: July 2016. 

[20] The Woman With Super Human Vision. BBC News online. Accessed: July 2016.

[21] Social media: 

Facebook: Colour Blind Awareness

See also