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.
I think forest green is a great one but on the other side of it, seafoam green is great too. 
My wife and I painted our room Tsunami which is like a dark deep blue with a hint of green. Do you listen to American HIp Hop band Death Grips? Such a trippy group.