Green swimming pool water is typically caused by green algae or a large amount of copper in the solution. You can tell the difference because while green algae prevents you from seeing to the bottom of the pool, copper still maintains clarity, however it still tints the water green.
To deal with green algae, first use pH reducer or pH increaser to get your pool to the desired pH level of between 7.2 – 7.6 ppm. Next, use pool shock (either Blast Out, Chlor-Burst, or Blitz). Be sure to wait for 8-12 hours to allow the chemicals to take effect, then use Halt 50 algaecide once per week. Doing so for a month should eliminate the green algae entirely.
Dealing with a high copper content in pool water is simpler. Begin by using Super Rust & Scale Remover in the morning. Let it sit for 24 hours, then adjust the chlorine and pH levels as needed. Once the pool water’s chemical composition is balanced, the green tint should be gone.