I do this alot with my embroidery. I love to shade the center of my flowers and the petals before I actually start the embroidery. I shade the animals too. Did a quilt with Bunny's with pretty little dresses on, for my new GGD, and even added pink on there cheeks.This adds dimention to your embroidery. I trace my pattern on my back ground, use my crayons to shade whatever area I want shaded, lay a paper towel over it and heat set with iron. Be careful about changing your towel often, because there will be wax on it from the crayons. Then I start my stitching. This I do by hand. I love doing hand work, its so relaxing.