Green water

[patricia]

We were away for 6 weeks and returned to a very swampy pool. We emptied and cleaned it, and are refilling it with a pristine clean filter. As it filled, the water was lovely and clear - sort of violet almost. Waking up this morning (it has been filling all night) the water is now a clear green. Any ideas what would make the water go green as it fills? There is no algae visible.