The most viable theory is that the crater has a large number of lime deposits and when there is a nearby tremor, this gets shaken up. It can also go brown overnight. That takes a few weeks before it changes back to normal. The interesting point is that no one knows why the lake changes colors at all. I'd like to see a good study, and I'd even be willing to help sponsor the research.
People say they are.
Once a lady came by and told me she wrote a book about the lake and that she would send me a copy. She never did. Researchers tell me about studies they are conducting, but again, the materials are never available to us who live here. There seems to be a lot of new developments occurring here. I see a lot of construction of homes and cabanas.