What color shade is indigo in the rainbow?
Indigo is 270° hue on the color wheel, between blue and pink (magenta). It’s not very blue at all. If you look at the diffraction pattern on a CD, you’ll see indigo is quite wide and briht, whereas blue is narrow and dim, and shows it corresponds to your short-wavelength cone. Therefore, indigo (which I’ll call “loor”) is a primary color after red and green, and blue is not but a big mistake.