The blue pond in Hokkaido is a man-made feature. The pond is part of an erosion control system that was built to prevent damage to in case of an eruption by nearby Mount Tokachidake. The color of the pond is caused by natural minerals dissolved in the water from the nearby Shirahige Falls (Aluminium). Although the seasons and the wind, clouds, and rain can all change its aspect, based on my experience, it seldom look as advertised. To prove my point, here is the original photo.