This is not an invention but a mind-blowing discovery which impacts human behavior in a strange way. There is a reason we see red as aggressive and dangerous color whereas blue as soft and trustworthy color. Sometimes you get up in the middle of the night to drink some water and in that darkness you could see every object around you as black and white or somewhat grey. And then you turn the light on, boom! you see every little color around you. Most of the men are just trichromatic, we can see the primary colors (red, blue and green). But few women are tetra-chromatic (including some kind of grey), now you know why men lag at identifying several colors in the spectrum.
How do we know sky is blue? How do we stop at the traffic light when it is red? Can we imagine this world without colors? Listen to episode-2 from knock-this-door podcast which was published on July 2019. This podcast is available in Tamil as well and you can listen to Vannam from Akkanna podcast.