Hey that's cool, I took exactly the same picture this summer. This is from the Corne de Sorebois, right? When I was there there was a little bit too much wind for the lake to be reflecting like in your picture, but it's still amazing to see this insanely blue-green billiard sheet between the mountains. Together with the view of several 4000-ers the Sorebois makes a very pleasant hike!
Anyway, nice shot,
Standing at the only street in Zinal that morning I was tossing coin between going to the Tracuit Hut or the Moiry Hut. The latter came up and the picture is taken during that rather long walk.
blue! Incredible he he he