The idea is to fill an area by coloring the fabric behind the embroidery. Usually, this means that only the outline is embroidered, with some details added. However, tinting isn't only for coloring inside the lines. Many artists use this technique to create spectacular backgrounds, borders, and accents for their embroidery work.
Color Outside the Lines Sometimes. In some circumstances, like this one, you can color outside the lines because you'll cut the piece out afterwards. This allows you to use large consistent strokes, as you can see in the red kidney above and on the right. This is an especially helpful tip for younger students who are coloring the organs in this My Body project. (Just be sure not to use this tactic on the upper half of the heart in the My Body book because we won't trim around all those veins and arteries.)