Now, let me tell you of another definition of tone, which again is included in our own. Some people will tell you that a picture is tonal, because there is some one prevailing hue of color in it. By “prevailing” we mean that some one color plays the most important part. In Vermeer’s picture, you may remember, it was blue. The girl’s skirt made a strong spot of blue. We are aware of other colors in the picture, but they play subsidiary parts. What we are most conscious of is a sense of blue throughout the picture--a prevailing tone of blue. So in Whistler’s _White Girl--Symphony in White, Number One_, there is a prevailing tone of white.