Postcard of Fountain Paint Pot photographed by Asahel Curtis, 1928. The Fountain Paint Pot is a mud pot located in Lower Geyser basin. It is named for the reds, yellows and browns of the mud in this area. The differing colors are derived from oxidation states of the iron in the mud. As with all hot springs, the heat in the caldera forces pressurized water up through the ground, which is expelled here. Also, rising gasses cause the bubbling action. The bubble action in the mud varies with the seasons. In the early summer, the mud is watery from the high water table due to rain and snow melt. By the end of summer, the mud is much thicker as the water table drops. Yellowstone National Park is a national park located primarily in the state of Wyoming, although it also extends into Montana and Idaho.