Blue is the color of light between violet and green on the visible spectrum. Hues of blue include indigo and ultramarine, closer to violet; pure blue, without any mixture of other colors; Cyan, which is midway in the spectrum between blue and green, and the other blue-greens turquoise, teal, and aquamarine.
Brown is a composite color. It is made by combining red and green, in specific proportions. In painting, brown is generally made by adding black to orange.