Why is purple not a color of the rainbow? Do we need indigo and violet?

Question

Basically what the title asks.

All the other colors of the rainbow are either primary or secondary. Violet is a shade of purple and (as I’ve always understood it) indigo is somewhere between navy and purple.

In: Other

Answer 1

Because it isn’t. When you look at visible light, there is no wavelength that corresponds to what we call “purple”. Our brains make it up, because different “sensors” in our eyes are being stimulated by a combination of other wavelengths. Violet light exists, it’s the light towards the very end of the visible spectrum beyond 380nm. You can choose to name it “Vurple” and the one you call purple something else, but that’s immaterial.