The photo above shows the brightly colored Grand Prismatic Spring in Yellowstone National Park, Wyoming. The red and yellow colors of the pool in the foreground contrast sharply with the azure blue color in the mid-ground and with the greens and tans of the slope in the background.
Red and yellow colors are caused by pigmented bacteria and thermophiles (heat-loving algae) inhabiting the hot spring. Specific colors of the thermophiles correspond to a particular temperature range of the naturally heated springs – temperatures are 160 F (70 C) at the spring’s source.
Colors are also a result of the ratio of chlorophyll to carotenoids – red/orange is observed during summer but typically, dark green is favored during the colder months. The inset photo shows a close up of a thermophile colony.