Grand Prismatic Spring in Yellowstone is the image you see on almost everything promoting the park. The image you see most often, though, is taken from the air. Unless you pay for an airplane or heli ride, you are out of luck to re-create that shot.
There is a trail that will gain you some elevation above the spring so you can shoot somewhat down on it. It is a bit of a booger. Straight up. Not fat friendly. I didn't go all the way up to the top. I got high enough to get above the trees and stayed low enough to keep my heart inside my chest.
Shooting this thing from above you need a few things to be in your favor. First, you need it to be a little windy. If it's not windy the steam from the hot spring just sits above it and blocks the spring. The wind pushes it out of the way. Secondly, you need sun. Afternoon sun is better. You would think softer light would be better, but I've tried it and it isn't near as vibrant.
Another thing that really helps when you are processing your image is the new Dehaze Tool in Lightroom. IN the case of these hot springs, it pretty much kills all of the haze caused by the humidity surrounding these springs.
I made this image with my Sony A77ii and Tamron 16-300mm lens. I'm glad I took that lens, because the composition I needed was just outside the range of my favorite landscape lens, the 24-70.