Human: Is the most expensive color in the world Blue? Assistant: 
Yes, Blue is the most expensive color in the world. Blue is a primary color. Blue is between violet and green on the visible light spectrum. Lapis Lazuli is used to make ultramarine. Ultramarine is a pigment of Blue Processing Lapis Lazuli into Ultramarine is the most expensive of color processes, so Blue is the most expensive color in the world.