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.
You know that varieties of the color red may differ in hue, chroma or lightness. 
Yes, The hue of a color is important. I like paining my house wall different colors of mostly shades of blue.
Hue
Hue is one of the main properties (called color appearance parameters) of a color, defined technically (in the CIECAM02 model), as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, green, blue, and yellow", (which in certain theories of color vision are called unique hues). Hue can typically be represented quantitatively by a single number, often corresponding to an angular position around a central or neutral point or axis on
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.