This is natural light pouring into the slot canyon around mid day, and is only visible at certain times of the year at that time of the day. The rock formations have been created by by eons of water erosion caused when the canyon floods. The colors are a natural feature of the rock layers' composition and the bouncing sunlight.
No HDR or texturing...just a bit of curves and contrast work, with some dodging and burning.
See other works from Antelope Canyon in my Arizona Set.