3.5: Color
Munsell Color System
Although first order assessment of color are useful for many purposes, the Munsell Color System is widely used to give specific names to the colors that naturally occur in rocks and soils. Specifically, you can order small, rugged booklets with color plates suitable for use in the field from numerous sources. The Munsell books allow you to give a specific name and code to each observed color (ex: Pale Yellowish Orange, 10YR 8/6).
The coded part of the system refers to three components of color:
- Hue refers to the actual color family, such as red, yellow, green, blue, etc. Hues are arranged in a circular format around a color wheel, with five principal hues (red, yellow, green, blue, and purple) along with five intermediate hues (e.g., YR) halfway between adjacent principal hues. In the case of pale yellowish orange - 10YR 8/6, the hue is 10 YR (10 parts yellow and one part red).
- Value represents the lightness or darkness of a color. In the Munsell system, this attribute is depicted vertically, with lighter colors at the top and darker colors at the bottom. The scale ranges from 0 (pure black) to 10 (pure white), with various gradations in between to show different levels of lightness. A value of 5 represents the true color. Value is given as the number before the slash. In the case of pale yellowish orange - 10YR 8/6, the value is 8.
- Chroma describes the vividness of the color; it is also referred to as saturation or intensity. High chroma colors are far away from the central axis and are vibrant and intense. Low chroma colors are close to the central axis and tend to be more muted or grayish. Chroma is designated with the number after the slash. In the case of pale yellowish orange - 10YR 8/6, the chroma is 6.
Color can be profoundly influenced by diagenetic processes and is typically something that is only described for mudrocks - we will discuss this more in detail in Chapter 5.
Readings and Resources
- Link to digital Munsell Rock Color chart
- Link to digital Munsell Soil Color Book
- Link to a website that converts from RGB to Munsell colors - https://pteromys.melonisland.net/munsell/