Green light has a wavelength of roughly 490-570 nm and is one of the additive primary colors, the complement of magenta. Many artists, however, continue to use a traditional color theory in which the complement of green is considered to be red.

Blue (from Old High German "blao" shining) is one of the three primary additive colors; blue light has the shortest wavelength range (about 420-490 nm) of the three primary colors

Indigo is the color of light between 440 to 420 nanometres in wavelength, placing it between blue and violet. Like many other colors (orange and violet are the most well-known), it gets its name from an object in the natural world - the plant named indigo once used for dyeing cloth.


