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> It’s a complex topic for sure. But the position of “color is purely a perception in our head and not wavelengths” position is too extreme in the opposite direction and isn’t helpful in building things.

As an illustration for the in your head position: Human eyes can't directly perceive yellow tones. What we think of as yellow is a computation on the signals of both the M and L cones. If both say they perceived radiation at approx. the same intensity, that gets calculated as yellow afterwards.

That's why RGB displays are not reproducing the correct wavelengths, but only those our eyes can read directly: red, green and blue.