Caño Cristales (English: Crystal Channel) is a Colombian river located in the Serrania de la Macarena province of Meta, and is a tributary of the Guayabero River. The river is commonly called the "River of Five Colors" or the "Liquid Rainbow," and is noted for its striking colors.
The bed of the river from the end of July through November is variously colored yellow, green, blue, black, and especially red, the last caused by Macarenia clavigera plants (family Podostemaceae) on the riverbed.
The quartzite rocks of the Serrania de la Macarena tableland formed approximately 1.2 billion years ago. They are a western extension of the Guiana Shield of Venezuela.
Caño Cristales is a fast-flowing river with many rapids and waterfalls. Small circular pits known as giant's kettles can be found in many parts of the riverbed, which have been formed by pebbles or chunks of harder rocks. Once one of these harder rock fragments falls into one of the cavities, it is rotated by the water current and begins to carve at the cavity wall, increasing the dimensions of the pit.
According to en.wikipedia