To change the type of pony, click the purple button. (If it says alicorn, it will switch to an alicorn once you click it.) The rest of the buttons are self-explanatory: the type button changes the style of that feature, the color changes the color, and the lighter/darker changes the shade of that color. Click "Reset" to go back to the original pony. And when you click the camera, it hides all the buttons. (There is a glitch where if you're at a unicorn then it shows a grey horn; get around it by clicking grey body then back to body color.)
Credit goes to lilystar5992 for making the original! I remixed it and fixed the glitch. I'll keep adding cutie marks (some will be very random), but if you have any suggestions type them in the comments! Here are the updates (I'll add them pretty frequently...) Update 1: I added a grey-scale body and a new grey eye color. There's a button for grey-scale hair but it doesn't work so don't try pressing it. (it works now, look ↓) Update 2: I added the grey-scale hair and two closed eyes (one with lashes and one without) Update 3: I added a "photo mode." Just click the camera and all the buttons will disappear. Note: Only press this when you're done, 'cause you'll have to start again if you press it when you're not ready. Update 4: Okay, forget the last sentence in update 3! When you press the cutie mark, all the buttons come back, so you don't have to worry about starting over!