Sudsy is drawn completely with yellow chalk. He main bubble body/head consists of a circle with a pair of eyes, a mouth, and a rectangular reflection mark on each side of his face (only 1 is shown at a time). He also wears a baseball cap worn backwards and is surrounded by much smaller bubbles that float up and shrink until they disappear (when he's not moving, only 6 bubbles [3 on each side] appear and float up and down continuously before they disappear when Sudsy moves again). Everything inside his main bubble, reflection mark, cap, and smaller bubbles is black like the chalkboard.
In Blue's Clues & You!, the chalkboard (and therefore Sudsy) is dark green, and his chalk outline is orange.