Why are indigo and violet in the rainbow and not just purple?
I always learned “ROYGBIV” as the colors of the rainbow. Red, orange, yellow, blue, indigo, violet.
What’s up with the last two? Isn’t indigo basically just dark blue? Why is it violet and not purple? Can’t it just be “ROYGBP”?
You are viewing a single comment
Actually, the answer turns out to be pretty interesting.
The short version is that what colors are considered "distinct" are heavily influenced by culture and Newton, from whom we get ROYGBIV, came from a culture which valued the dye called "indego."
Edit: It also seems Newton thought the number 7 had cosmic significance and thought there ought to be 7 colors.
More info in this short video: https://www.youtube.com/watch?v=bf7WT6TLy8s
Well it was the 1600s and he was a natural philosopher. Back in those days, all sorts of weird stuff ended up in the books because it fit a certain philosophy. Our modern understanding of empirical science is a relatively new idea.