– the dark blue dye obtained from the indigo plant

– a color between blue and violet in the spectrum

“the deepest indigo of the horizon”

Indigo is defined as a main color. It’s an official part of the classic rainbow and of the visible color spectrum created by Issac Newton from 1666–72.

Indigo, however, is a mystery.

Originating from the plant indigofera, and originally being used for textiles, the color has been long circulating the globe. The point of contention with the color rests in whether indigo should be it’s own color or an official part of of the color spectrum.

…or something like this:

Indigo, being a color directly between blue and violet, is so close to both colors that it’s often never recognized as indigo. As a result, many believe that indigo was never deserving to be it’s own color group. It’s a common belief that indigo isn’t it’s own color, but is instead just a variation of blue or violet, and should reside in one of those categories.

There is speculation that Newton only included indigo in his original spectrum findings in order to have seven colors, because he believed he needed specifically seven colors for them all to be able to combine and create white. Other’s believe Newton only singled out indigo because Newton was following the age-old pattern of sevens: the seven days of the week, the seven main planets in our solar system, etc.

However, as Newton was a renowned scientist, many believe that he was correct in his findings.

Theories that support Newton include the wavelength of indigo. On the visible color spectrum, each of the seven colors has a specific range of wavelength. Indigo’s rests around 425–445nm. This is a smaller range than other colors. Red, for example, rests at around 625–740nm and green rests at 520–565nm. While there are such colors with a larger range, not all are so large. Yellow rests at 565–590nm, which is only a 25nm span, 5 off from the 20nm span of indigo. These details support the idea that NThe truth is not proven though. Newton’s real intent of including indigo in his original color spectrum is unsure. All that we truly know is that indigo is so similar to blue and violet that it’s hard to distinguish the color from them at all. And as to whether or not it scientifically deserves to be a part of the modern color spectrum? That’s still up to debate.ewton noticed indigo had a large enough wavelength to be it’s own color.