Indigo is a color that is traditionally regarded as a color on the visible spectrum, as well as one of the seven colors of the rainbow: the color between blue and violet. Although traditionally considered one of seven major spectral colors, sources differ as to its actual position in the electromagnetic spectrum. Indigo is a deep and bright color close to the color wheel blue (a primary color in the RGB color space), as well as to some variants of ultramarine.
The color indigo was named after the indigo dye derived from the plant Indigofera tinctoria and related species.
The first known recorded use of indigo as a color name in English was in 1289.