I start out with white foam. The bottom of the abdomen is colored with a Pantone art marker color #101-T pale yellow. You can also use a yellow Sharpie, but you have to color it, then wipe it off while it is wet until it fades to the desired shade. The top of the abdomen is colored with a Pantone as well, color #119-T medium olive, then a single dot of brown Sharpie on top of each segment of the ab.