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What is color blindness?

1 in 12 men and 1 in 200 women are color blind so statistically speaking the average person may know at least 25 people who are color blind! If you know of a loved one or friend with color blindness, let them know about EnChroma eyewear for color blindness.

Color (color) blindness (color vision deficiency, or CVD) affects approximately 1 in 12 men (8%) and 1 in 200 women in the world. In Britain this means that there are approximately 3 million color blind people (about 4.5% of the entire population), most of whom are male. Worldwide, there are approximately 300 million people with color blindness, almost the same number of people as the entire population of the USA!

There are different causes of color blindness. For the vast majority of people with deficient color vision the condition is genetic and has been inherited from their mother, although some people become color 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, medication etc.
Most color-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 color blindness and there are extremely rare cases where people are unable to see any color at all.

The most common form of color blindness is known as ‘red/green color blindness’ and most color-blind people have one type of this. Although ‘red/green color blindness’ is a common term, there are different types and severities of it. Being ‘red/green color blind’ doesn’t mean people with it mix up red and green only, it means they can mix colors which have some red or green as part of the whole color. So someone with red/green color blindness will probably confuse blue and purple because they can’t ‘see’ the red element of the color purple. See the example of pink, purple and blue pen cases below to understand this effect.

Types of Color Blindness

There are several types of inherited color blindness.


Normal color vision uses all three types of light cones correctly and is known as trichromacy. People with normal color vision are known as trichromats.

Anomalous Trichromacy

People with ‘faulty’ trichromatic vision will be color blind to some extent and are known as anomalous trichromats. In people with this condition all of their three cone types are used to perceive light colors but one type of cone perceives light slightly out of alignment, so that there are three different types of effect produced depending upon which cone type is ‘faulty’.

The different anomalous conditions are protanomaly, which is a reduced sensitivity to red light, deuteranomaly which is a reduced sensitivity to green light and is the most common form of color blindness, and tritanomaly which is a reduced sensitivity to blue light and is extremely rare.

The effects of anomalous trichromatic vision can range from almost normal color perception to almost total absence of perception of the ‘faulty’ color.
People with deuteranomaly and protanomaly are collectively known as red-green color blind and they generally have difficulty distinguishing between reds, greens, browns and oranges. They also commonly confuse different types of blue and purple hues.

People with reduced blue sensitivity have difficulty identifying differences between blue and yellow, violet and red and blue and green. To these people the world appears as generally red, pink, black, white, grey and turquoise.

See the dichromacy images below – about half of people with anomalous trichromacy will see the world in a similar way to those with dichromacy but their ability to perceive colors will improve in good light and deteriorate in poor light. Often their color perception can be as poor as it is for those with dichromacy.
People with anomalous dichromacy can have either inherited color blindness, in which case their ability to see colors will remain the same, or they can have acquired it, in which case their condition could get worse, or possibly improve over time.


People with dichromatic color vision have only two types of cones which are able to perceive color i.e. they have a total absence of function of one cone type. Lack of ability to see color is the easiest way to explain this condition but in actual fact it is a specific section of the light spectrum which can’t be perceived. For convenience we call these areas of the light spectrum ‘red’, ‘green’ or ‘blue’. The sections of the light spectrum which the ‘red’ and ‘green’ cones perceive overlap and this is why red and green color vision deficiencies are often known as red/green color blindness and why people with red and green deficiencies see the world in a similar way.

People with protanopia are unable to perceive any ‘red’ light, those with deuteranopia are unable to perceive ‘green’ light and those with tritanopia are unable to perceive ‘blue’ light.
People with both red and green deficiencies live in a world of murky greens where blues and yellows stand out. Browns, oranges, shades of red and green are easily confused. Both types will confuse some blues with some purples and both types will struggle to identify pale shades of most colors.

However, there are some specific differences between the 2 red/green deficiencies.


Protanopes are more likely to confuse:

  1. Black with many shades of red
  2. Dark brown with dark green, dark orange and dark red
  3. Some blues with some reds, purples and dark pinks
  4. Mid-greens with some oranges


Deuteranopes are more likely to confuse:

  1. Mid-reds with mid-greens
  2. Blue-greens with grey and mid-pinks
  3. Bright greens with yellows
  4. Pale pinks with light grey
  5. Mid-reds with mid-brown
  6. Light blues with lilac


The most common color confusions for tritanopes are light blues with greys, dark purples with black, mid-greens with blues and oranges with reds.
The images show how the beautiful colors of the pigments are lost to people with each type of dichromatic vision.

Color blindness

Monochromacy (achromatopsia)

People with monochromatic vision can see no color at all and their world consists of different shades of grey ranging from black to white, rather like only seeing the world on an old black and white television set. Achromatopsia is extremely rare, occurring only in approximately 1 person in 33,000 and its symptoms can make life very difficult. Usually someone with achromatopsia will need to wear dark glasses inside in normal light conditions.

The EnChroma Color Blind Test is specifically designed to determine your type of red-green color blindness (deutan or protan) and level: mild deutan or protan, moderate deutan or protan, or strong deutan or protan. However, there are limits to what can be tested with a self-administered online test. If you believe that you may have a color vision deficiency, EnChroma recommends getting a complete eye exam by a qualified eye care professional.

Take the Color Blind Test