How to show color shade changes in pen drawing

Through the secret of the line and the lightness of the brush strokes to show the color shades.

Generally light-colored areas have sparse lines and are drawn with a single stroke using a smoother technique, thus the lines drawn are thinner. In the drawing of dark areas or contours of the shadow, the dense grid drawing to make the color channel contrast, the darker the place of the grid drawing the more dense, and by repeating the drawing to make the line thicker and deeper. By doing this, you can show the color shades very well.