text: Dissolved and particulate material in water can cause it to be appear more green, tan, brown, or red. For instance, dissolved organic compounds called tannins can result in dark brown colors, or algae floating in the water (particles) can impart a green color. Color variations can be measured with reference to a standard color scale. Two examples of standard color scales for natural water bodies are the Forel-Ule scale and the Platinum-Cobalt scale. For example, slight discoloration is measured against the Platinum-Cobalt scale in Hazen units (HU).
  The color of a water sample can be reported as:
  * Apparent color is the color of a body of water being reflected from the surface of the water, and consists of color from both dissolved and suspended components.  Apparent color may also be changed by variations in sky color or the reflection of nearby vegetation.
  * True color is measured after a sample of water has been collected and purified (either by centrifuging or filtration). Pure water tends to look cyan in color and a sample can be compared to pure water with a predetermined color standard or comparing the results of a spectrophotometer.
  Testing for color can be a quick and easy test which often reflects the amount of organic material in the water, although certain inorganic components like iron or manganese can also impart color.
  Water color can reveal physical, chemical and bacteriological conditions. In drinking water, green can indicate copper leaching from copper plumbing and can also represent algae growth. Blue can also indicate copper, or might be caused by syphoning of industrial cleaners in the tank of commodes, commonly known as backflowing. Reds can be signs of rust from iron pipes or airborne bacteria from lakes, etc. Black water can indicate growth of sulfur-reducing bacteria inside a hot water tank set to too low a temperature. This usually has a strong sulfur or rotten egg (HS) odor and is easily corrected by draining the water heater and increasing the temperature to  or higher.  The odor will always be in the hot water pipes if sulfate reducing bacteria are the cause and never in the cold water plumbing. Learning the water impurity indication color spectrum can make identifying and solving cosmetic, bacteriological and chemical problems easier.