Green water This is caused by planktonic algae and indicates a high phosphorus level. It requires a granular and liquid algaecide to control it. Another thing that will get rid of planktonic algae is a UV sterilizer.
Brown water This usually occurs in the fall and is due to discoloration from leaves and debris. That is a temporary water color and can be improved once you remove the leaves from the water feature.
White water This is due to a bacterial bloom. Nothing that can be done for this, but to be patient. The water is not contaminated.
Black water This is due to contaminents in your backyard garden water feature. This usually happens when there is no skimmer box installed or no mechanical water filtration. With very little bio filtration, the debris adds up in the bottom of the pond. There is no quick fix for this problem. You have to drain the water feature and start over again.