Viewed from the side, the water likely looked clear and colorless. But viewed from above, you probably did see color—green or blue for tap water, and possibly yellow or brown for natural samples.
Many people are surprised to find “clear” water looking blue-green. The blue-green color that appears and strengthens with increasing depth arises from an intrinsic property of water—its tendency to absorb light at the red end of the visible spectrum.
White light is made up of all different colors of light. As white light passes through increasing depths of water, it loses more and more red light to absorption, and the remaining light looks increasingly blue-green. You might have noticed this before in a bathtub full of water.
This blue-green effect is, er, muddied if the water is turbid—that is, containing mud, algae, or other sediments. In turbid water, the light scattered off this particulate matter will overwhelm the water’s natural blueness and appear brown, yellow, or green.