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.
Then you can also create a texture effect. Just cover the drawing with a light stroke first then follow with rough, think strokes to serve as details . texture. This can also be applied when you're using colored pencils. And you can also create a light, smooth look with crayons. Just color your drawing with very rough and thick strokes (this might make the drawing look messy at first) then rub off the excess color with cotton or scratch paper.