Colour Test
Test how well you see. The pictures consist of hundreds of small dots of different colours. People with normal sight can see numerals in the different pictures.
Colour vision is possible thanks to the two forms of light-sensitive cells on the retina of the eye. They are called rods and cones. The rods are sensitive to light and help us see in the dark. The cones react to the different wavelengths of light, meaning we can see different colours. There are three types of cone: one that reacts to the colour blue, one that reacts to red and one that reacts to green. The colours we see are a combination of the different primary colours in an additive colour scale. They are known as RGB (red, green, blue) colours. When they mix, they create the secondary colours cyan, magenta and yellow. Mixing all the colours creates white.
If a person is colourblind, the cones do not work properly. A person who is colourblind may also lack certain cones. This means that they cannot see the colours on the wavelength the cone is receptive to, and so the actual colour blends into another colour. The most common form of colourblindness is when a person cannot tell the difference between red and green.