Grayed paint mixtures formed by scraping your palette and mixing the scrapings into a unified gray. You can keep the scrapings together into families so you end up with a series of different colored muds. For example, cool light mud, warm light mud, violet mud, green mud, and so on. Use these muds to create beautiful grays in your painting against which you can show off your purer more saturated colors. This creates a much more powerful impact. Sometimes I re-saturate (see saturation) them with parts of my pure pigment piles. This prevents the mud getting too neutral. Muds are beautiful provided you put them in the right place!