It would be nice to at least have the 7 colors of the rainbow available to us.
They are also used in science, in the electromagnetic spectrum, they are used in the Chromatic scale used for notation in music.
You actually already have 6 of the rainbow colors. You are missing INDIGO (dark blue).
Here is a Wikipedia article showing the seven rainbow colors: https://en.wikipedia.org/wiki/Rainbow#Number_of_colours_in_spectrum_or_rainbow