When we look at any object, we can tell the colour of it. If two people with normal vision look at same object, they both spell out the same colour. But they both may or may not have the same COLOUR in their brain.
Quite confusing right… Let’s take an example, if two people are looking at an orange object, then one person fix a colour in his mind say “X”, the other may have a colour say “Y” fixed, but these both have learned that X= Orange and Y = Orange respectively in their minds.
Our colour vision starts with the sensors in the back of the eye that turn light information into electrical signals in the brain – neuroscientists call them photoreceptors. We have a number of different kinds of these, and most people have three different photoreceptors for coloured light. These are sensitive to blues, greens and reds respectively, and the information is combined to allow us to perceive the full range of colours. Most colour blind men have a weakness in the photoreceptors for green, so they lose a corresponding sensitivity to the shades of green that this variety helps to distinguish.
At the other end of the scale, some people have a particularly heightenedsensitivity to colour. Scientists call these people tetrachromats, meaning “four colours”, after the four – rather than three – colour photoreceptors they possess. Birds and reptiles are tetrachromatic, and this is what allows them to see into the infrared and ultraviolet spectra. Human tetrachromats cannot see beyond the normal visible light spectrum, but instead have an extra photoreceptor that is most sensitive to colour in the scale between red and green, making them more sensitive to all colours within the normal human range. To these individuals, it is the rest of us who are colour blind, as while most of us would be unable to easily distinguish an exact shade of summer-grass-green from Spanish-lime-green, to a tetrachromat it would seem obvious.
So, let me know what do you think?