Earth tone

Earth tone is a color scheme that draws from a colour palette of browns, tans; any of various rich colors containing some brown. The colors in an earth tone scheme are muted and flat in an emulation of the natural colors found in soil, moss, trees and rocks. Earthtone colors come from natural things around us: brown soil, green leaf, sky, as well as the red sun. These palettes can create a warm, nature-friendly atmosphere Natural tones are also considered "Earth tones".

From factmonster.com:

"Neutral colors don't usually show up on the color wheel. Neutral colors include black, white, gray, and sometimes brown and beige. They can be created by mixing two complementary colors or combining a pure color with white, black, or gray. Pure neutral colors include black, white, and all grays while near neutrals include browns, tans, and darker colors.'"

Many earth tones originate from clay earth pigments, such as umber, ochre, and sienna.

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Wikipedia