Just an optimistic thought here...perhaps your pool looks green due to the reflection of the now-green trees vs. the barren trees of winter . You mentioned your pool sits at the edge of the woods.

My own pool has an ever-so-slight greenish cast to it in places due to the reflection of trees. I have to look to places where there's no tree reflected to see the true color of the water and to convince myself that my pool really isn't having a problem.