Where in this photo can I find archaea?
It's probably the yellow bacterial mats, which are rich in life. The mats are a stratified ecology which varies with distance from the surface, so they are rich in many species of algea, procarote and eukariote. In Yellowstone,  the bacterial mats can range in color including brown, green, yellow and orange. They are different to precipitated minerals. 

You can say "The photographer contains archaea"! So, no need to search very far. 

Here is a pic of an bacterial mat habitat: https://www.sciencedirect.com/science/article/pii/S0717345817300738

You can see in some videos. Ideally we would have a a biology video demonstrating the stuff at Yellowstone to show if it's squishy, slimy, spongey, has growth rings, colord layers, cross sections... although it's only tourist videos for the moment.