system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we have a color wheel, with purple next to red, and describe purple as a mix of red and blue, when the color spectrum has red at low frequencies and purple at high?

EDIT: Thanks for the replies!  Follow-up question: So if I understand correctly, we evolved 3 color receptors. They're pretty good at telling us if something is dark, red, between red and green, green, between green and blue, and blue depending on what combination of receptors are firing. But we can get even more bandwidth out of this codebook if we could use the red+blue combination, so the red receptor evolved the ability to respond to high and low frequencies, inventing purple? (I'm simplifying by talking about the receptors as if their activation was binary on/off.)
gpt
There is a distinction between purple and violet.

Violet is what you see in the color spectrum / rainbow. Violet is a color directly associated with high-frequency (short wavelength) visible light (any higher and you go into ultra-violet).

Violet can look similar to purple and the terms 'violet' and 'purple' are often used interchangeably - but there is a technical difference.

Purple does not appear in the rainbow / color spectrum. Purple has no specific frequency / wavelength of light associated with it. Instead, purple is a combination of lower frequency light (red colors) and higher frequency light (violet colors) which your brain interprets as a purple or magenta color. So if you have a material that reflects some lower frequencies and some higher frequencies it will appear purple to you.