On our autumn tree I determined that the very bright yellow leaves catching the late day sun were a bit too bold.
So my plan was to soften the yellow with its complementary color, purple. See below the bright yellow leaves near the point of the pastel pencil.
Softening the color and brightness of pastel is best accomplished by using a pastel pencil or a hard pastel such as the NuPastel brand.
I applied the purple pastel pencil lightly over the yellow spot, rubbing back and forth gently. Here is the result:
All set! Notice that the basic hue (yellow-orange) did not change. This is also a technique that can be used to help convey shade.
So next time you want to soften a color or create distant (vs. local) colors, which are more muted than your bold foreground hues, use the complementary color by scumbling, cross-hatching or blending into the color you desire to change.