What we were taught
Remember the science teachers saying sunlight is white? Is it though? Is the Sun yellow? What is even “colour”? Why do we perceive different frequencies of the electromagnetic spectrum as different colours?
To be honest, no one knows why these frequencies show us the exact colours they do, but what we can do is to imagine how it so happened in Humans, or life on earth in General.
What we weren’t taught
The Sun emits electromagnetic radiation, whose peak frequency is that of the colour yellow. Now what that means is that the maximum amount of radiation emitted by the Sun is Yellow. Let’s look at the visible spectrum:-
The yellow light at about 510 Terahertz lies almost in the middle of the spectrum. When the eyes of our ancestors saw this, they adapted to it being the primary focus for them to recognise, and so adapted for other wavelengths around to be visible as well, such that they could distinguish the yellow very clearly. The main aim back then was to find where the sun is, finding light meant food for the new water animals, as it would be where the plants grew. It meant navigation and differentiating day from night.
Slowly and steadily the functions evolved as our needs evolved, and as life moved from water, to land, and to air.
So you can say that we see the colours as they are just because the Sun emits radiation whose peak frequency is around Yellow! If we evolved near a Red Dwarf, we’d have seen different colours, more around red, maybe we’d never be able to see Blue, but we could see infrared frequencies as different colours.
New colours altogether! Now that is something to think about!