Indigo

Indigo is a deep blue-purple color name, associated with both a natural textile dye and a proposed band of the visible spectrum.

Color: Color is the visual experience produced by light interacting with the eye and brain. Indigo is one color category within human color experience.
Indigotin: Indigotin is the blue organic compound primarily responsible for the color of indigo dye. This molecule gives natural indigo its characteristic blue appearance.
Indigofera tinctoria: Indigofera tinctoria is a tropical legume cultivated as a major source of natural indigo dye. Its leaves have supplied indigo dye across South Asia and beyond.
Blue: Blue is a color category spanning hues associated with shorter visible wavelengths than green. Indigo is commonly treated as a deep or violet-leaning blue.
Visible spectrum: The visible spectrum is the range of electromagnetic wavelengths detectable by human vision. Indigo is often placed among the named colors of this spectrum.
Vat dyeing: Vat dyeing colors fibers with a water-insoluble dye temporarily converted into a soluble form. Indigo is applied to cloth through reduction and oxidation in a dye vat.
Woad: Woad is a European plant whose leaves yield blue dye through a process related to indigo production. It was a major European blue dye before imported indigo became dominant.
Violet: Violet is a spectral color at the short-wavelength end of visible light, beyond blue. Indigo is often distinguished from violet by being bluer and less red.
Hue: Hue is the aspect of color associated with distinctions such as red, green, and blue. Indigo names a hue, though its precise boundaries vary.
Leuco-indigo: Leuco-indigo is the pale, soluble reduced form of indigotin used during dyeing. Exposure to air converts it back to blue indigotin on the fiber.

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