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Red-Green Colour Blindness

Red-Green Colour Blindness

Colour blindness, also known as colour vision deficiency, is a condition in which a person finds it difficult to identify or differentiate between certain colours. Red-green colour blindness is more specific to red and green and their related hues. It occurs more commonly in men than in women, but first, let us understand colour identification in humans better.

Red-Green Colour Blindness

Every colour that humans can identify is a combination of 3 basic colours: Red (R), Green (G) and Blue (B). Every colour contains red, green and blue (R, G, B) to different extents on a scale of 0 to 255. For instance, red is (255, 0, 0), green (0, 255, 0) and blue (0, 0, 255). Yellow is (255, 255, 0), magenta (255, 0, 255) and orange (255, 165, 0). Yellow, magenta and orange have a component of red in them. Yellow and orange also have a component of green in them but no blue whereas magenta has a component of blue along with red in it.

Causes of red-green colour blindness

It can be of two types:

  1. Acquired:
  • As an outcome/after effect of another disease such as diabetes
  • Due to certain medication like a few used to treat neurological disorders
    Exposure to chemicals such as carbon monoxide can
  1. Inherited:
  • One may be born with the color vision deficiency

Inherited red-green colour blindness favours males over females. The reason lies in the genetics: each human cell has 23 pairs of chromosomes. One particular pair determines gender: so a female has all “XX” chromosomes, and whereas males have one “XY” pair. The first component of the pair (X) comes from the mother, and the second (X or Y) comes from the father. Genes are the building-blocks of chromosomes. It turns out that the mother is the carrier of the red-green colour blindness defective gene(s). A female will have red-green colour blindness only if both XX have the defective red-green colour blindness gene(s); for a male, it is sufficient for only the X (from the mother) to have it.

Example Effects

A person with red-green colour blindness can confuse between red (255, 0, 0) and yellow (255, 255, 0) traffic lights if different RGB hues of these colours are used, because they are adjacent. He/ she may also fail to differentiate between several shades of colours of a 12- or 24-colour pencil set.


Common clinical tests for red-green colour blindness are:

  • Isihara Color Test (literate population)
  • Farnsworth Lantern Test (for young children)
  • HRR Color Test

There is no medical cure for red-green colour blindness. However, one being in the know of the condition in case you suffer from it can help make appropriate lifestyle and professional adjustments. Optometrists may also prescribe pigmented contact lenses & other aides that can partially improve discrimination of some colors, but can cause failure to identify certain other hues altogether. To further know how to deal with this vision deficiency, consult an Ophthalmologist.

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