They call it the blues...
Blue is a color, an emotion and a form of American music. It is a primary color that mixes with two other primary colors to create a myriad of colors.
As a standalone color it is one of the most popular "favorite" colors. Everyone has a different concept of what feeling it evokes for them. "Feeling Blue" represents the down side of life. On the other hand it is an optimistic pigment, the hue of the sky is the limit, you can go as far and as fast as you want to go.