Blue
A primary colour between purple and green
Is the most expensive color in the world Blue?
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.
What was the most expensive pigment used by Renaissance painters? Is #1 a shade of the color blue?