There are generally two scenarios in which you may see discolored water at your tap.
The color of water is caused by naturally occurring compounds from decaying vegetation and organic matter that enters source water through runoff, falling vegetation, etc. While discoloration is rarely a health concern, it is an aesthetic concern. Color is measured in platinum-cobalt units (PCUs). Charleston Water System’s lab is equipped with state-of-the-art spectrophotometers to obtain exact color level measurements.
A second common reason for discolored water is when the fire department conducts their semi-annual flow test of each hydrant. This will occasionally stir up the water in the line for a short period of time. You can clear your supply by flushing your water until it is clear again.