The simultaneous presence of feces, urine, and blood in the stall of a truck stop bathroom. Like other rainbows, the Truck Stop Rainbow only appears when the proper conditions exist. Blood-laced feces, bloody noses suffered as part of a massive colon evacuation, accidentally peeing blood, involuntary defecation and urination as a result of injury, and open sores can all contribute to the formation of the Rainbow.
Opening a bathroom stall and finding the floor soaked in urine and errant feces, and the toilet itself bespecked in fecal bits, mini puddles of urine, and dots of blood indicating an anal spray pattern. This is certainly a sighting of a rare Truck Stop Rainbow}