How did the color of the water in Lake Nyos change following the release of the carbon dioxide gas, and what caused this change in color?

The water in Lake Nyos is normally a beautiful, deep-blue color. However, the post-eruption of Lake Nyos made the water murky reddish brown. This is apparently formed by the oxidation of iron-rich bottom waters that were carried up to shallower lake levels during the hydrovolcanic eruption. It had been known for years that the water in Lake Nyos was extremely enriched in dissolved CO2 at the bottom of the lake. Thus, a CO2 "eruption" occured.