ROY G BV? Like Pluto from the planets, indigo has been booted. Some say it should not have been included in the first place.
Isaac Newton is credited with listing the order of the colors in the spectrum of visible light — red, orange, yellow, green, blue, indigo, violet.
There have been protests about the inclusion of indigo. Indignant, Goethe wrote a book in 1810 describing simple experiments that proved there are three primary colors and three secondary. Indigo didn’t make the cut.
There was speculation that Newton was influenced by the significance of the number seven in the bible, or that he wanted to show the connection between sound waves and light waves, and thus named seven colors to parallel the seven notes in the musical scale.
In any case, indigo’s persistence in the lineup serves as a reminder that visible light is like race: a continuum, not discrete colors; and its beauty gives lie to the notion that the word primary is anything more than a label.