What else are you putting in the water? Tri chlor? If so, there may be copper in that, but not enough I would think to make it turn green...Maybe its the end result of chlorine eating up some organics. That can sometimes give you a tinted water color until it clears up. Maybe post some chem levels - FC TC TA PH, etc

We have high iron content and any time we add our well water to top off, more sequesterant goes in, especially if we have to shock for any reason. Our first fill with the new pool last year left it looking like chocolate syrup after shocking. Lately, so much rain has gone in we don't even have to consider the hose - we are pumping out instead of adding.