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Colour Deficiency
Colour is used widely in materials used in the classroom today. It is important that teachers and
parents understand the special needs of colour deficient children and what can be done to help
them in their learning.
For some colour deficient individuals, the names red, orange, yellow, and green are simply
different names for the same colour. The same is true for violet, lavender, purple, and blue.
Among the colours most often confused are pink/grey, orange/red, white/green, green/brown,
blue green/grey, green/yellow, brown/maroon, and beige/green. Pastels and muted tones are
difficult to distinguish. The colour vision defect may be so bad that the affected person cannot
distinguish brown socks from green socks, a red traffic light from an amber one, or green grass
from brown soil by colour alone.
There are broadly three types of colour deficiency, or ‘colour blindness’- protanopia,
deuteranopia and tritanopia. Generally, being colour blind does not mean that no colours are
seen (except in very rare situations – this is called ‘achromatopsia’) but rather that there is some
confusion with certain colours.
Red–green deficiencies
In both protanopia and deuteranopia and their related conditions, red and green are confused.
This is due to a problem with the cone cells, those cells in the retina that are responsible for
seeing colour, among other roles. To distinguish red from green, the brain relies on the
difference in stimulation of medium- and long-wavelength pigments in the cones. Red and
green are not the only hues affected. Some researchers believe that people with red–green
colour-vision deficiency actually see shades of beige, yellow, or orange in place of red and/or
green.
Protanopia
A person with protanopia is a protanope or a protan. Protanopes cannot distinguish reds and
greens; reds, moreover, appear dark. If you’re missing long-wavelength pigments in your cones
but you have medium-wavelength pigments, you’re a protanope. Those medium-wavelength
pigments are not very sensitive to long wavelengths (the reds), so the hues that usually would
be described as’ red’ do not look red and seem dark compared to other colours that are actually
equally bright.
Deuteranopia
This is the most common form of colour blindness. A person with deuteranopia is a deuteranope
or a deutan. Deutans, like protans, cannot distinguish reds and greens. Unlike protans, though,
there is no brightness deficiency. Hues that people with normal colour vision would describe as
‘red’ do not appear red to a deutan, but they don’t appear darker than other colours that are
actually equally bright. Deutans can have such good colour discrimination that they can pass a
standard colour-blindness test.
Tritanopia
A significantly rarer colour-vision deficiency is tritanopia. This is a condition where blues and
greens are confused. Tritanopes or tritans have no sensitivity to short wavelengths, broadly
equivalent to blue. Tritanopia is quite rare in its hereditary form, but some diseases, including
diabetes, induce tritanopia in people who formerly had normal colour vision. Among elderly
people, “acquired” tritanopia is more common than the hereditary kind.
‘Normal’ colour vision
protanopia
Tritanopia
Achromatopsia
deuteranopia
Helping those with Colour deficiencies
 Label a picture with words or symbols when the response requires colour recognition.
 Label colouring utensils (crayons, coloured pencils, and pens) with the name of the colour.
 Ask a classmate to help colour deficient students when work requires colour recognition.
(for example, colour coding different countries on a world map.)
 Teach colour deficient students the colour of common objects. Knowing what colour things
are can help them in their daily tasks. Example: when asked to colour a picture, they will
know to use the crayon labelled green for the grass or blue for the sky.
 Try teaching children "all" the colours. Remember, most colour deficient children can
identify pure primary colours. It is normally just different shades or tints that give them
problems. If they cannot learn certain colours, let them know you understand that some
colours look the same to them, and it is "OK".