Actually, the main pigmenting (coloring) agents in soils are organic matter, iron, and, to a lesser extent, manganese. When these agents are not covering the mineral grains, the natural color of the grains is visible. Colour is a simple method of classifying soil. Black/dark brown soil usually indicates the presence of decaying organic matter so is generally fertile. Pale brown/yellow soil often indicates that organic matter and nutrients are low and this generally means poor fertility and structure.he colour of the soil varies from one place to the other because soil is formed out of different types of rock . Since rocks are of different colours and textures , the colour of the soil varies from one place to another .
