A mixture of small story's and poems
Each and every day in the rainbow factory the whistle screams louder than Canterlot voice, yelling at the workers to start working, gears turning and creaking and the screams echoes the factory, engraving the memory unto pony's who foolishly agreed to work in the factory and they would relive the memory each night haunting the workers until the day they die. You can hear the bones grinding, cracking the bones of young colts and mares who the judges deemed unworthy to live in cloudsdale. The colors you see in the 'wondrous machine' is nothing but red blood that goes into rainbows and if the Pegasus know where colors for rainbows came from the memory of siblings who didn't pass would haunt the pegasus from generations to come and the rainbows they see is nothing but crimson red and they know who to blame for their pain and misery about the pony's they care about and would tear down the factory in the name of their loved ones and only then, the workers would be set free from their iron shackles an chain with a heavy ball at the end, unfortunately no one knows about the nature of their beloved factory and the blood rainbows.