We are taught growing up that water is blue, but some rivers are black, brown, emerald blue, green, or even blue-green. So what gives these rivers their colors? First we need to understand what color is. Natural light is actually made up of a number of different colors associated with different wave lengths within the light spectrum. Think of the multiple colors of light when refracted by a prism. The color we associate with anything is the range of light waves that is reflec