Marco Polo was the first to report on the preparation of indigo in India, “being made of an herb which they place in a great vessel, then pour in water, and leave it till the juice is given out.”
Indigo occurs between 420 and 450 nanometers in wavelength on the electromagnetic spectrum, placing it between blue and violet.
In New Age philosophy, indigo is regarded as representing intuition. Electric indigo represents the sixth chakra, called Ajna, which is said to include the third eye. This chakra is related to intuition and gnosis, insight into the divine and infinite.
Ancient Egyptians used indigo-dyed cloths to wrap their mummies.
Ibn el-Baitar, a 13th century Andalusian scientist, botanist, pharmacist and physician, recommended a solution of indigo (Indigofera) to soothe all tumors and abscesses, and that a weak solution dissolved in water and taken internally lessened not only pain but even sexual desire. He quotes another author who suggests that India or Kirman indigo, when added to a rose conserve, will check both stupidity and sadness, and that a concoction of indigo, lead monoxide, pepper, rose oil and wax will calm palpitations. A lotion of indigo, plantain oil, and honey is recommended for gangrene.
Sir Isaac Newton picked indigo as the seventh shade to make up his mystical harmony of colors. He assigned indigo A on the musical scale.
David André, a merchant-dyer who settled in Nimes in the early 17th century, created a sturdy cotton twill dyed indigo which came to be known as Serge de Nimes, which was later shortened to de Nimes, and finally, denim. Levi Strauss added rivets in the 1920s.
During the restoration of Vermeer’s Girl with a Pearl Earring in 1994-1995, it was ascertained that Vermeer had originally given the background a deep greenish tone by glazing a very transparent layer of indigo mixed with weld (a natural yellow dye-stuff obtained from flowers of the wouw or woude plant as it is called in Dutch), over the dark black underpainting. Mixed together with a binding medium such as linseed oil they form a transparent greenish tone.
Pliny mentions the use of pigeon droppings to lighten indigo to a blue.
Joan Míro’s Tempest-Indigo consists of a green figure with a single eyeball. The eyeball hangs defiantly, a searching engine, an organ of imperial design, a living emblem of vision, amid an energetic jungle of green, a tangle of lines and webs, with a section below, a patch of white occupied by black squiggles, the background in indigo.
Carlo Crivelli (c1435-c1495), mixed indigo with lead white for the bands of pale blue and gold decoration on the throne and steps in The Virgin and Child with Saints Francis and Sebastian.
Matisse’s Seated Nude includes a square of indigo to the left of the woman’s head, a bright yellow L accenting its lines, and the blue next to it of an open window, the presence of a soft velvet night, the air in the room full of vibrancy and warmth.
“Mood Indigo,” a jazz composition with music by Duke Ellington, was the first time Ellington had written intentionally for radio broadcast. He turned the trumpet, trombone, and clarinet “upside down,” assigning high notes to the trombone and low notes to the clarinet. The arrangement produced some interesting overtones on the electronic microphones.
The Indigo Girls are an American folk rock duo consisting of Amy Ray and Emily Saliers.
Turbulent Indigo, an album by Joni Mitchell, references a great deal of pain, madness and death, and won a grammy in 1994.