What is colour blindness?
Sometimes a person may not have as many of the different types of cone cells, or they may be missing altogether. This means that some people cannot see some colours.
Some people may be unable to see the colours green and red – this is the most common type of colour blindness. They might see red as orange and green as white.
Some people may have cones missing which cause them to be unable to see blue and yellow.
How your eyes see colour
Light from the sun or from a light bulb bounces off everything that your eyes see and goes through the pupil (the black hole in the centre of the front of your eye).
The light reaches the retina, which is like a movie screen at the back of your eye.
How do you get colour blindness?
Defective colour vision, as it is called by doctors and scientists, is something which is passed on in the genes. That means that a person gets it from his parents, and they got it from their parents.
Most of the people with colour blindness are male – about 1 boy in 10 will be colour blind, while only about 1 girl in 200 will be colour blind.