Here’s another step-by-step to show you the layering process I do for just about everything (multiple, transparent layers of color). In this case I used watercolors and pencil and I printed out the worksheet on white card stock (the kind you get at any office supply store).
1. First I colored in my 16 shapes with transparent watercolor washes of yellow, blue and magenta. I used a #12 round watercolor brush. The paint was watered down A LOT so that the colors were kind of “pastelly.”
2. Once the first layer of watercolor was dry (this is very important!), I added a second layer of watercolor over all the colored parts. I used a watered-down brown for the second layer.
3. Here it is with the second layer (brown) applied. Even though it looks so much darker than the first image, the brown layer was very light. It’s the combination of the two colors that make it darker.
4. Once the second layer of watercolor was dry (again, completely dry!), I added shading in the “corners” with a mechanical pencil:
a. Scribble a dark mass of pencil in the deepest part of the corner.
b. Now fan it out with a lighter touch.
c. Finally, take your index finger and smudge it. Really rub it in!
5. In this scan the top half has the shading and the bottom half doesn’t (to better illustrate the effect).
6. And here it is with shading in all the corners.