If water is clear or colorless, why is snow then white? Actually, snow can take on other hues depending on certain conditions, just like when water has certain impurities (like when a river turns muddy).
We see snow in the first place because of light, as light is reflected off the surface of the ice crystals. Most all of the white light that comes from the sun hitting the snow will reflect back and still be white light. Therefore, snow on the ground appears to us as white.
However, you will find that glacial ice will often take on a blue color. This is because it is not the same as snow. As light enters a deep layer of ice, the light gets bent causing more and more of the red end of the light spectrum to be absorbed. As these more red wavelengths are absorbed, more blue wavelengths are available to reflect back to your eyes. The color of glacier ice will then appear to us as blue.
In some instances, impurities in snow are the reason why snow sometimes shows us a different color. For instance, algae can grow on snow making it appear more red, orange, or green. Dirt and debris near a road on the other hand can make snow appear gray or black.