Indigo

This article is about the color. For other meanings, see indigo (disambiguation).

Indigo is the color of light between 440 to 420 nanometers in wavelength, placing it between blue and violet.

Indigo is neither an additive primary color nor a subtractive primary color. It was named and defined by Isaac Newton when he divided up the optical spectrum (which is of course a continuum of frequencies). He named seven colors specifically to link them with the (known) planets, days of the week, notes in the octave, and other lists that had seven items.

The human eye is relatively insensitive to indigo's frequencies, and some otherwise well-sighted people cannot distinguish indigo from blue and violet.

Color coordinates