Why is indigo, a blue-violet, a tertiary, listed in the visible spectrum? One can understand the primaries; red, blue, and yellow, and the secondaries; orange, green, and violet being listed into the visible spectrum, but not just one tertiary. If we are to going to list indigo, a tertiary, then we must list and give names to all the tertiaries in the visible spectrum.

We must list red-orange, orange-red, orange-yellow, yellow-orange, red-yellow, yellow-red, yellow-green, green-yellow, green-blue, blue-green, violet-green, green-violet, red-violet, violet-red, violet-blue, and blue-violet, which is already incorporated, and must include all the rest of the tertiaries in the visible spectrum.

Then explain how red-orange will have a longer wavelength than orange-red because red is more dominant in red-orange than orange-red. This is based on red having a longer wavelength than orange. And red has a longer wavelength than red-orange. Green-blue has a longer wavelength than blue-green because green is more dominant in green-blue than in blue-green.

This is based on green having a longer wavelength than blue. Explain how yellow-green has a shorter wavelength than orange-yellow, because orange has a longer wavelength than yellow and green. Explain how violet-blue has a shorter wavelength than blue-violet because violet is more dominant in violet-blue than in blue-violet. This is based on violet having a shorter wavelength than blue.

Therefore, we should have the electromagnetic spectrum explain all these combinations of tertiary colors and their relation of shorter and longer wavelengths to each other and of course still include the primary and secondary colors and their wavelength relations to each other. Then also include all the shades and tints of all the primary, secondary, and tertiary colors and all their wavelength relations to each other.

Then include the neutrals, black and white, and their wavelength measurements in relation to each other and all the primary, secondary, and tertiary colors, shades, and tints. In general, try to relate every color and every color combination in existence, including the neutrals, and every single wavelength measurement relation to one another.

This would be a true representation of wavelength relations between the entire visible light spectrum, which is between ultraviolet and infrared; and simply, just a more accurate representation of the visible light spectrum in general.