Let's first start with using crayons. It's usually one of the first coloring material introduced to little children because it's perfect for kids to use since there's jumbo sized ones that they can easily handle without breaking it in half. It's also a great material for bigger kids and even grown_ups because it has a wide range of colors to choose from.
A Variety of Pressure Creates Emphasis. If there are some areas you want to accent, you can press a little harder on the crayon and end up with a darker, more intense color. This is another good reason to color lightly for full coverage. For example, in this picture of the heart below, I pressed harder when tracing the lines within the heart and in the vein and artery openings. I did the same thing when coloring the muscles and the brain.