Was pi invented or discovered?

[Angrboda]

"Red" is not an intrinsic property of light, it's merely a way for humans to describe how our eyes perceive certain wavelengths.

Actually, for us it is. The light is processed by our retinas for all intents and purposes as if it was actually made up of RED, GREEN and BLUE. Of course there are still no primary colours, and you're right that colour is just a wavelength, however that is in fact how we see the world, and why colour-blindness typically affects one of the colour processors in our brains.