Black and white. According to the inquiry of personal library, the finishing touch is a sketch created by Xu Beihong, with the creation time of 1922 and the specification of 6 1cm× 45cm. The picture shows that a bird of prey suddenly rushed out of the wall, which frightened the people who looked at the picture. In the painting, the person is wearing a gown, holding a brush, standing with his arms slightly tilted, staring at the dragon. Sketching refers to drawing an object with a pencil or charcoal pen, spreading it out with lines, and then drawing it in black and white, so "making the finishing point" is black and white.