The major colors of the rainbow are red, orange, yellow (equal amounts of red and green), green, cyan (equal amounts of green and blue including some shades such as teal or aqua), blue (confused for indigo when it was first discovered but is actually blue), indigo (between the blue and violet bands), and violet (not to be confused with purple).
The infra reds and ultra violets are beyond the scope of the rainbow but may be seen by other species and converted to colors in the readable band using special processing.
The one major color that's not in the rainbow is the magenta color (including shade variations such as purple, fuchsia and pink).
Purple is often mistaken as being the same as violet, but purple is created by mixing equal amounts of red with the blue wave but with a color dark enough (1/4 to 1/2 of the strength) to distinguish itself with fuchsia, which is made with full strenghs of the red and blue waves, and pink, which is fuchsia with 1/2 the strength of the green waves. Some websites make violet look like a reddish violet and indigo look like violet with no hint of blue.
A band of major colors not in the rainbow include brown, grey, white and black.