Turquoise Lake along Icefields

A view of a lake along the descent from Bow Summit.
The turquoise color comes from the rock flour suspended in the lake. The rock flour comes from the glaciers grinding over the rocks as the glacier is pulled down the mountain by gravity. Meltwaters from the glacier drain into the lake carrying the ground up rock into the lake.
A common myth is that lakes are blue because they are reflecting the color of the sky. Lakes are blue because when the sun's rays reflect off the bottom of the lake, only the blue wavelengths have enough energy to reflect all the way back to the lake surface where the color can be seen . Blue is the shortest wavelength in visible electromagmetic spectrum and therefore has the highest energy of visible light. In a lake that has rock flour suspended in it from a glacier draining into it, some of the sun's rays are reflected back by the rock flour instead of being reflected by the bottom of the lake. Still, all the other colors of the visible light spectrum are absorbed except for green. Green has the second most amount of energy and is the next color down from blue in the light spectrum. Mixing green and blue colors together creates the turquiose color. The more active the glacier, the greener the water. Glacier fed lakes such as Lake Louise actually get greener as the summer progresses.