Most pressure washers come with a variety of nozzles, each color-coded to a particular spray pattern. Here are general guidelines: The red nozzle creates a very focused, powerful stream of water. It’s best used for spot-cleaning very tough stains or dried materials on hard surfaces, such as concrete or steel.  The yellow nozzle creates a 15-degree angle of spray, which is a narrow fan suitable for removing dried mud, tough stains, rust, mildew, or paint off sturdy surfaces, such as concrete or metal.  The green nozzle creates a 25-degree angle of spray. This is the general-use nozzle and is suitable for blasting away mud, leaves, and other grime from decks, walkways, siding, fences, and driveways, as well as for cleaning boats, automobiles, and outdoor furniture.  The white nozzle creates a 40-degree angle of spray, which is gentle enough for use cleaning delicate items, such as flower pots, windows, blinds, and automobiles. It’s also very useful for quickly rinsing objects.  The black nozzle creates a large, 65-degree fan of water. This nozzle is typically used with detergents.