There are times when your swimming pool will change colors after adding chlorine or shocking your pool. The colors may vary from green, red, brown, purple or black. The reason behind this color change usually indicates the presence of minerals (metals) in your swimming pool. The chlorine added to the swimming pool oxidizes the metals and will cause a chemical reaction that becomes visible in your swimming pool.
While there are treatments that can be added to your pool to clear the problem, you may also want to find out what the source of the metals in your swimming pool. Metals in your pool water may come from several sources. If you water comes from a well, then you may want to check metal content in your well. City water may have traces of metals due to old rusty pipes that are going from your treatment center to your home. Other sources may be pumps, heaters, old copper piping and algaecides.
In general, a greenish tint to the water usually indicates that your water may have either copper or iron. If it is a deep thick green and your water is starting to cloud up. There is probably an algae in your pool and you should follow these steps.
CLICK HERE FOR HOW TO CLEAN A GREEN SWIMMING POOL