Here's the standard color wheel set to Red, Blue, Yellow as primary colors.

You'll notice that magenta is represented as almost a whole different color. It's light red in the CMYK, light purple in RGB.

And

Cyan, baby blue, sky blue, etc. isn't represented. Instead you get a blue-purple they call violet.

Light Red - Magenta

Light Blue - Cyan

Blue-Purple - Indigo

Light Purple - Red-Purple - Fushsia

We as a whole can't decide what constitutes purple/violet in RGB model

Even if someone doesn't know what a true "Indigo" looks like they are still experiencing that color for what it is. They will just call it Bluish-Purple or Purplish-Blue. And unless it really was the exact mix of 50/50 blue and purple it wouldn't be indigo. It would be a equivalent to a Redish-Orange. A Bluish-Indigo or Purplish-Indigo.

Sorry for the walls of text I was learning and thought I might as well share.