Not exactly at Mammoth, but instead of starting a separate thread thought I would add this here. IIRC (notes are at home) this is at Norris Geyser Basin. I loved the colors as I shot this and struggled mightily last night to recreate them in the resulting image. Here at least the sun wasn't so high, and the orange tints took advantage of the lower light. The steam conveniently blocks a lot of people in the background....
I know a lot of folks love Yellowstone in B+W, but don't shortchange those colors.