b'Its more prevalent in EuropeansTest yourselfThe most common test for colour because they were westernisedblindness is the Ishihara test. Within these patterns are dots which form a earlier. If you were a fruit pickernumber visible to those with normal and you couldnt see the colourcolour vision. Can you see them?of the fruit, you were less likely to survive.responsible for colour vision. Each contains visual pigments sensitive to wavelengths of lightred, green and blue.Most people can match all colours of the spectrum by mixtures of only these three fundamental colour sensitivities. The huge variety of colours we perceive comes from the cone cells response to different compositions of wavelengths of light. Defects in colour vision occur when one of the three cone cell colour coding structures fails to function properly. One of the visual pigments may be present and functioning abnormally. Or, it may be absent altogether.The cones with the blue are almost always normal, says Molly. So blue deciencies are very rare. Its the red/green spectrum thats affected by the colour channels. Fortunately the blue/yellow channel remains pretty much unaffected.The condition is far more prevalent in men than women, with only 0.4percentofEuropeanfemalesbeingcolourdecient.Thats because the condition is linked to the X chromosome. Women have two Xs. If women have one good X, then theres no problem. Because men only have one X, they get the colour deciency.Molly says its thought theres an evolutionary explanation to why we and western cultures have a higher rate of colour blindness than, say, the Japanese, of whom ve percent are colour blind. Its more prevalent in Europeans because they were westernised earlier and there was no selection against colour deciency. If you were a fruit picker and you couldnt see the colour of the fruit, you were less likely to survive. For most people with colour blindness, it can be frustrating and occasionally dangerous, depending on the severity of the condition. Trafc lights are not so bad because colour blind people get to know the position of the colours. But sometimes caution lightswhen there is just one light that could be red or greencan cause a problem. Buying brightly coloured clothes can also be challenging. Many men depend on their wives or partners for colour choices, says Molly. You should see 12, 74, 6 and 2.29'