The Munsell color system is based on the work of Professor Albert H. Munsell. It mimics the HSB color model, but is more empirical in its approach. Munsell colors are represented by three values: hue, value and chroma.

Hue is represented by an angle from 0 to 100, or relative to the nearest of 10 major colors, such as red (abbreviated R), yellow-red (YR), yellow (Y), etc.

Value is how bright the color is, and is represented by the vertical axis. This scale goes from 0 (pure black) to 10 (pure white) with intermediate shades in between.

Chroma is the saturation of the color, or how pure it is. This axis goes from the center of the Munsell color space (neutrals, or grays) to the outside of the shape (the most vivid, saturated colors). The length of this axis varies with each combination of value and chroma. Some colors may only extend to 4, while colors with very rich flourescents may be as high as 30. As new paint colors are developed this axis may expand. It's the variability in this axis that gives the Munsell color space its unique, uneven shape.

3D representation of the Munsell color model. The vertical axis represents value (or brightness) and ranges from 0 (black) to 10 (white). Distance from the center represents chroma (or saturation). Values start at 0 (gray) and go to anywhere from 4 to 30, depending on how saturated the color can get. The angle around the middle represents the hue (or color).	One wedge of the Munsell color model. Chroma increases horizontally, and value vertically. Colors with a red border indicate paint colors that cannot accurately be reproduced on an rgb monitor (approximated colors are shown). These diagrams only extend to a chroma value of 16 despite some colors extending well beyond this limit.

Some have questioned the validity of the Munsell color system in regards to how well it represents human color perception, as in this article.

For more information on the Munsell color system, visit the GretagMacbeth website.

Sources: GretagMacbeth.com