Mr. Blue
Mr. Blue lives alone in a one-storied house. EVERYTHING he has is blue. His grass is blue, his lamps are blue, his clothes are blue, his furniture is blue, his food is blue, his walls are blue, his floors are blue, his garden is blue, his skin is blue! What color is his staircase?
He doesn't have a staircase, because he lives in a one-storied house.