I think blue is one of the best of the three primary colors, color theory is very fascinating to me.
I agree but I always get confused, what are the other primary colors?
Red Green and Blue make the set of primary colors, as they are the most prominent in the gamut of color spectrum ranges.
Out of the primary colors, I think green would be my favorite. 
I love DEEP greens. Sage specifically. The hue is just so powerful and bold in tone.