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.
For a much lighter effect, you can mix a small amount of soft pastel with baby powder and apply it with cotton balls. This technique is usually used for gradient backgrounds. Lastly, enjoy your work! You can keep it in your portfolio folder or hang it on your wall. There are still a lot of ways to use coloring materials in order to give life to your drawings. Just don't be afraid to explore.