What is your favorite color? Mine is blue.
Its blue because of the spectrum of visible light.
 I do not remember the science behind the light spectrum. My car is blue so that is why I like it.
Is well know that Blue is one of the three primary colours of pigments in painting and traditional colour theory
That is correct. I also like the color red.
Shades of red
Varieties of the color red may differ in hue, chroma (also called saturation, intensity, or colorfulness) or lightness (or value, tone, or brightness), or in two or three of these qualities. Variations in value are also called tints and shades, a tint being a red or other hue mixed with white, a shade being mixed with black. A large selection of these various colors is shown below.
Notable tints of red.
Notable tints of red Pink.
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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.