Click the green flag to start. Click on colors to change the color of the pencil. Space bar to change the coloring page. The "Clear" button to start over, and naturally the smaller and bigger buttons, to, well, make it smaller and bigger.
Update: I added the slider, it doesn't do anything yet. Once it works I will remove the smaller and bigger buttons. :) Here's what I added (and what I intended to add.) I added a smaller/bigger pencil button. I wanted to make it so that you had to color in the lines. turned out this was a backdrop and not a sprite, and it had a white background anyways so if I made the pen go to the back layer you couldn't see it because of the white background.