The Prism Hercudrome is a rainbow-colored Hercules beetle found within the Ancient Forest, zone 1 (far southeast section, a dead-end with flower beds). It can primarily be found during dusk/dawn, so should the time not be set up for you, be sure to exit, perform an investigation of some kind, or something in order to pass the time and try again. Once you've met the time requirements, head to this location with the Capture Net primed. You should see a discoloration on a tree on the western side of the dead-end, which will be the beetle. Should it not be there, simply leave and set the time back up somehow to set the conditions up once more. It will net you 500 RP as well as this trophy.