A good scientist can tell a lot of things by just looking at the color of the soil.
For example, a very black soil generally contains more organic matter (dead plant and animal matter) than a brown soil. Organic matter is good for the soil.
Also, reddish soils get that way from iron minerals. The red color is caused by the “oxidation” of iron--the same thing that causes iron or steel to rust. Water and air move through these soils pretty easily.
If a soil is gray or blue-gray, it shows that water and air do not move easily through the soil. Gray soils are old and tired out. They have very little organic matter and cannot grow plants very well.
Scientists use a chart to check the color of soil. The color tells you a lot about soil.
Photo: USDA NRCS