Indigo is a deep, resonant blue-violet color, the ninth degree in the King Scale of Colour. The name derives from the Greek indikon (Ἰνδικόν, "Indian dye"), borrowed into Latin as indicum and later into Middle English, referencing the prized source of the dye: plants of the Indigofera genus. Pure indigo sits at the perceptual boundary between blue and violet, near the 420–450 nanometer range of the visible spectrum.

Position on the Tree of Life

Indigo in the King Scale corresponds to the sephirah Yesod, the ninth sphere on the Tree of Life. Yesod is called "The Foundation" and is the sphere of the Moon, the astral light, and the storehouse of images and dreams. As the color of this sphere in the King Scale, indigo evokes the twilight atmosphere of the lunar world—reflective, illusory, yet structurally essential. It is the color of the veil between the astral and the material, the deep indigo of the night sky just after sunset.

Astrological and planetary correspondence

Indigo belongs to Luna (the Moon). In the Queen, Emperor, and Empress scales, Yesod also receives violet or purple tones, but the King Scale‘s indigo emphasizes the cold, reflective, and hidden aspects of lunar influence. It is the color of the moon‘s shadow side, the light that is not its own.

Historical context

Indigo‘s significance predates its codification in magical color scales. As a dye, it was known in antiquity: Herodotus mentions its use by the Britons for body painting; Pliny the Elder notes indicum as a precious import from India. In medieval alchemy, indigo was associated with the lapis philosophorum in its early, dark stages—the nigredo giving way to a blue-violet hue that signified the emergence of the albedo. The 18th-century discovery of "indigo" as a distinct spectral band by Isaac Newton (who added it to his original five colors to make seven) fixed its place in Western color theory. Crowley's 777 adopts the King Scale from the Golden Dawn's color attributions, where indigo becomes the exact color of Yesod‘s active masculine expression: the foundation from which all form arises, and into which all form dissolves.

In this table cell, indigo appears as the King Scale color for the ninth step (Yesod). It also appears on the Tree of Life as the color of Paths 26 and 32, reinforcing its lunar and reflective character across different contexts in the same handbook.