Although you can mix pastel colors, the more colors you have to start with, the easier it is to get all the colors you want through blending. A good pastel set has at least three values of each color and at least three values of gray. A pastel technique you can use to expand your range of values, is to add neutrals to your colors, mixing them together directly on the painting surface. Add white to tint a color (making it lighter in value), add gray to tone a color (creating a medium value), and add black to shade a color (achieving a dark value).