Soil comes in a rainbow of hues, from chalky white through yellow, orange, and brown to nearly black. The color of soil is determined by its mineral and organic makeup, its drainage condition, and the degree of oxidation or extent of weathering.
Light-colored surface soils are low in organic matter and often coarse in texture. Pale soils frequently are highly leached, meaning that many of their nutrients have been washed away by water over the years. These light soils are often found in areas with high average temperatures.
A dark soil color can indicate a high organic content or it may mean poor drainage, low average temperatures, or other causes of slow oxidation of organic matter.
Mineral content affects subsoil colors, turning them yellow, red, or brown. Topsoil can also reflect its mineral makeup; a high iron content, for example, results in red soil.