Swimming pool stains make pool cleaning jobs much harder, affecting the pool's overall cosmetic appearance. Most of the time, simple brushing or scrubbing won't do the trick. The first step to removing these stains is identification. Stains can result from metals, rust seeping through the wall or some organic material. However, the color of the stain will tell a whole lot about its type. Greenish-brown, earthy colored stains are almost always something organic, usually resulting from decaying leaves or other organic material.