Once the pump and filtration stop a swimming pool will turn a dark green with streaks of light green, orange and black within about 2 weeks. You can dump a heavy dose of shock in it to slightly prolong but without movement the water turns bad quickly.
I found this out when someone stole my pool pump, filter and the electrical box off the side of my house.
WOW! They will steal anything now days.
Note my post to Kart. I would use my Berkey water purifier to make good drinking water out of contaminated swimming pool water.