YInMn Blue, also known as Oregon Blue or Mas Blue, is an inorganic blue pigment that was discovered by Mas Subramanian and his (then) graduate student, Andrew Smith, at Oregon State University in 2009. The pigment is noteworthy for its vibrant, near-perfect blue color and unusually high NIR reflectance. The chemical compound has a unique crystal structure in which trivalent manganese ions in the trigonal bipyramidal coordination are responsible for the observed intense blue color. Since the initial discovery, the fundamental principles of colour science have been explored extensively by the Subramanian research team at Oregon State University, resulting in a wide range of rationally designed novel green, purple, and orange pigments, all through intentional addition of a chromophore in the trigonal bipyramidal coordination environment.

Blue is one of the three primary colours in the RGB (additive) colour model, as well as in the RYB colour model. It lies between violet and cyan on the spectrum of visible light. The term blue generally describes colours perceived by humans observing light with a dominant wavelength that's between approximately 450 and 495 nanometres. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering. An optical effect called the Tyndall effect explains blue eyes. Distant objects appear more blue because of another optical effect called aerial perspective.