How is your colour vision?

July 10, 2015

Though most people have some form of colour-blindness, more severe versions can affect your job qualifications or your abilities to do certain every-day tasks. 

How is your colour vision?

Testing for colour-blindness

  •  If you have a problem distinguishing colours or an eye condition that impairs colour perception, your optometrist may check your colour vision as part of your eye exam.
  • You must also have this checked if you are planning to do a job that requires good colour vision.
  • The most common test is a series of pictures of coloured dots in which numbers or shapes are picked out in different colours. People with different forms of colour-blindness may be unable to distinguish these from the background pattern.

How does colour-blindness happen?

  • Colour-blindness occurs when some of the cones — the light-sensitive cells in your retina that detect colour and are responsible for daylight vision — are either missing or not working properly.
  • It is much more common in boys than girls, affecting between eight and twelve percent of boys but less than one percent of girls. Colour-blindness is usually inherited, so most affected people are born with it — though it is frequently not picked up until someone notices, say, that a child persistently colours the sea pink or confuses the purple crayon with the blue one.
  • About 99 percent of all of those people affected have a form of red–green colour-blindness. Its severity varies — many colour-blind people are able to see some shades of red and green, though they may have difficulty distinguishing between them.
  • Being colour-blind does not increase your risk of other eye conditions but it sometimes poses practical frustrations. It may be difficult to distinguish red from green apples or to tell the difference between, say, ketchup and chocolate sauce. More seriously, it can be hard to tell when meat is cooked properly. Matching socks or other clothes, reading maps, home decorating and harvesting strawberries can also cause problems. Some colour-blind people find it difficult to see computer screens clearly.
  • Colour-blindness won't prevent you from driving. Red and amber traffic lights may look similar, and green may appear dirty white, but the position of the lights will signal their meaning quite clearly — though you may not be able to tell which is lit until you are quite close.


  • Although there is no cure, colour filters and tinted contact lenses can improve colour differentiation and contrast for some people.
  • If you start to find it difficult to distinguish colours that you used to be able to tell apart, have a checkup.
  • Some diseases, medications, industrial or agricultural chemicals and eye injuries can trigger colour-blindness, which may improve through treatment of the disease or by stopping exposure to the drugs or chemicals responsible.
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