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

Like all man made classifications, it’s an arbitrary choice. Color is a spectrum, not a 7-step scale