Colour blindness (colour vision deficiency, or CVD) affects approximately 1 in 12 men (8%) and 1 in 260 women. This means that in New Zealand there are approximately 200,000 colour deficient people (about 4.5% of the entire population), most of whom are male.
There are different causes of colour blindness. For the vast majority of people with deficient colour vision the condition is genetic and has been inherited as a recessive x-linked gene from their mother, although some people become colour blind as a result of other diseases such as diabetes and multiple sclerosis or they acquire the condition over time due to the aging process or medication side effects, among other causes.
Most colour blind people are able to see things as clearly as other people but they are unable to fully ‘see’ red, green or blue light. There are different types of colour blindness and there are extremely rare cases where people are unable to see any colour at all.
The most common form of colour blindness is known as red/green colour blindness and most colour blind people suffer from this. Although known as red/green colour blindness this does not mean sufferers mix up red and green, it means they mix up all colours which have some red or green as part of the whole colour. For example, a red/green colour blind person will confuse a blue and a purple because they can’t ‘see’ the red element of the colour purple. See the example of pink, purple and blue pen cases below to understand this effect.
Similar problems can arise across the whole colour spectrum affecting all reds, greens, oranges, browns, purples, pinks and greys. Even black can be confused as dark green or dark blue.
The effects of colour vision deficiency can be mild, moderate or severe so, for example, approximately 25% of colour blind pupils currently leaving secondary school are unaware that they are colour blind, whilst 60% of sufferers experience many problems in everyday life.
Statistically speaking most people with a moderate form of red/green colour blindness will only be able to identify accurately 5 or so coloured pencils from a standard box of 24 pencil crayons. Depending upon which type of the condition a colour blind person is suffering from they could see the set of pencil crayons similarly to the following images.