More information about rods and cones
In this colour-enhanced microscope image, the rods are green and the cones are blue.
Cones are present at a low density throughout the human retina, but with a sharp peak in numbers at the centre of the fovea. Rods are present at high density throughout most of the retina, but with a sharp decline in the fovea.
The distribution of red, green and blue cones in the fovea of a person with normal eyesight. (Very few blue cones)
Cones are divided into three types – simply put, a cone can “see” only one colour: red, or green, or blue, so they are divided into red, green and blue cones. This refers to the colour each can see, NOT the colour of the cone itself. Cones are actually transparent, although they are often illustrated as being coloured.
The 4.6 million cones in a human retina are not divided equally between red, green and blue: about 64% are red, 32% are green, and just 2% are blue. The blue cones have the highest sensitivity and are mostly found outside the fovea.