Munsell color system (English Wikipedia)

(Munsell 1905), ch.2, pg. 18 Munsell, Albert H. (1905). A Color Notation. Boston: G. H. Ellis Co. Munsell's original description of his system. A Color Notation was published before he had established the irregular shape of a perceptual color solid, so it describes colors positioned in a sphere.
(Munsell 1905), ch.3, pg. 28 Munsell, Albert H. (1905). A Color Notation. Boston: G. H. Ellis Co. Munsell's original description of his system. A Color Notation was published before he had established the irregular shape of a perceptual color solid, so it describes colors positioned in a sphere.
(Munsell 1905), ch.4, pg. 41 Munsell, Albert H. (1905). A Color Notation. Boston: G. H. Ellis Co. Munsell's original description of his system. A Color Notation was published before he had established the irregular shape of a perceptual color solid, so it describes colors positioned in a sphere.
(Munsell 1905), ch.1, pg. 7 Munsell, Albert H. (1905). A Color Notation. Boston: G. H. Ellis Co. Munsell's original description of his system. A Color Notation was published before he had established the irregular shape of a perceptual color solid, so it describes colors positioned in a sphere.

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Centore, Paul (December 2012). "An open-source inversion algorithm for the Munsell renotation". Color Research & Application. 37 (6): 455–464. doi:10.1002/col.20715.
Klink, Galya V.; Prilipova, Elena S.; Sobolev, Nikolay S.; Semenkov, Ivan N. (2023-10-01). "Perceptual variance of natural soil aggregates with the Munsell soil colour charts by unexperienced observers: Case study for diverse soils". Geoderma. 438: 116645. Bibcode:2023Geode.438k6645K. doi:10.1016/j.geoderma.2023.116645. ISSN 0016-7061.

Munsell, Albert (10 October 2012). "How Is the Munsell Hue Circle Relevant to Your Work". Munsell Color System; Color Matching from Munsell Color Company. X-Rite inc. Retrieved 18 February 2025. He wanted to use a decimal system making each step divisible by 5 or 10—a system which is easy to understand and easy for computer programming and cataloging. That's why Munsell used 5 principal hues—red, yellow, green, blue and purple—instead of the seven colors in the visible spectrum (ROY G BIV).