Vision and how we see the world is wildly complex. I learned this back in art school and it has always stayed with me.
For example, in a rainbow there is no pure purple (aka magenta). It does not exist as a wavelength of light. Purple is a color our brain just kind of makes up. This happens when only two of three kinds of nerve cells (cones) in our eye are stimulated.
This video by Steve Mould and The Royal Society explains the whole thing super clearly.
Curiously there scientists are looking for women believed to genetically have a fourth yellow cone. These women would see more colors than the rest of us!