Blue is one of the three primary colors
Is it? I had no idea!
Blue
Blue is one of the three primary colours of pigments in painting and traditional colour theory, as well as in the RGB colour model. It lies between violet and green on the spectrum of visible light. The eye perceives blue when observing light with a dominant wavelength between approximately 450 and 495 nanometres. Most blues contain a slight mixture of other colours; azure contains some green, while ultramarine contains some violet. The clear daytime sky and the deep sea appear blue because of an optical effect known as Rayleigh scattering.
color printing, the shade of cyan called process cyan or pigment cyan is one of the three primary pigment colors which, along with yellow and magenta, constitute the three subtractive primary colors of pigment. (The secondary colors of pigment are blue, green, and red.) As such, the CMYK printing process was invented in the 1890s, when newspapers began to publish color comic strips.
Process cyan is not an RGB color, and there is no fixed conversion from CMYK primaries to RGB. Different formulations are used