The Doctor posed a new riddle and demanded that I figure it out before he would allow me to leave the tower. I don't think he gave me enough to go on, but he insists that I have all the facts I need. Can anyone help?

Three monstrous demons, Hellios, Terminos, and Sanguinos, stand before the hellish gates of the underworld. They each have horns, wings and tails of three different colors, red, black and green. Between the three of them they posses one physical attribute of each of the three colors. If Hellios has green wings and Terminos has red horns, what color tail does each demon have?

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