This was one of my favorite things to do as a kid! All you need is a piece of thick paper, a bunch of old crayons (especially black), and a large paperclip.
First, color a thick layer of your favorite different colors in a detailed pattern (it can be anything) on the sheet of paper. Press on the crayon heavily , so none of the paper is showing. It should be thick and waxy when finished.
Next, color a thick layer of black over every part of the colorful pattern you just created. Apply the crayon heavily so it covers all the colors. Open one side of the paperclip and use the point to scratch out a picture or pattern. The best part is that if you don’t like something, just color over it with black crayon and try again.