The most outstanding feature of colored pencils is their use in subtle optical color mixing. Because colors cannot be mixed prior to applying they must be combined on the support through means of shading and cross-hatching. Colors are built up in layers of continuous single-color shades or crossed lines of different colors creating the tone of the drawing.
Sgrafitto is the technique of laying down one ore more layers of color and cutting through the topmost layer to expose the colors underneath. After building up color, especially dark color, you can gently gouge it with a blade, fingernail, toothpick or any sharp instrument. Scraping the surface with a broad edged tool will expose large amounts of base color.
Frottage is rubbing made by placing a textured object under your paper and rubbing the paper with your pencil.
Glazing is the technique of drawing an image using just one color in a full range of tones and then working over the top using another color. This produces a brilliant range of original and tertiary colors.