blue is one of the 3 primary colors
Oh wow, I didn't know that! What other colors are primary colors?
the human eye perceives blue as dominant. it is the most important of the primary colors
Actually, what is a primary color?
An optical effect called Tyndall scattering explains blue eyes. Distant objects appear more blue because of another optical effect called aerial perspective.
Blue has been an important colour in art and decoration since ancient times. The semi-precious stone lapis lazuli was used in ancient Egypt for jewellery and ornament and later, in the Renaissance, to make the pigment ultramarine, the most expensive of all pigments. In the eighth century Chinese artists used cobalt blue to colour fine blue and white porcelain. In the Middle Ages, European artists used
Secondary color
A secondary color is a color made by mixing of two primary colors in a given color space.
Additive secondaries.
Additive secondaries Light (RGB).
For the human eye, good primary colors of light are red, green, and blue. Combining lights of these colors produces a large range of visible colors.
That is, the primary and secondary RGB colors (with secondary colors in boldface) are: 
Combining RGB colors means adding light (thus the term "additive color")