All of the Red Rocks "clue box" pictures, and RAYYo running look like they are from the southeast "corner entrance" at the bottom of the amphitheater.
There are two entrances at the bottom of Red Rocks -
Left hand side bottom, (as you face east, looking DOWN at the stage) -- IIRC does NOT have heaps of handrails up the side like RAY & Yo are near.
Right hand side bottom is typically where the band buses / equipment and stuff gets offloaded. Also, when you go "backstage" It's through the right hand side -- the wheelchair access ramps, IIRC are on the right. The left has some sharp steps up and I think there is a sign that says no wheelchair access as they don't have an ADA compliant "ramp" on that side. That looks like Ray and Yo entrance point.
The amphitheater is situated between two big rocks -- I think they are called Creation Rock and Ship Rock. If you go to the redrocksonline site, they have a little video, and maybe someone smart can tell if, when they get to the "keep it pure" picture at the end, if the big rock piece you see jutting up and taking most of the pic could be the one behind E/J and BJ & Tyler -- if so -- the tallest part is at the top of the amphitheater, the parking area is called the Top Circle lot --