The eraser button erases and click the paint splotches to change the color. Sorry there isn't many colors, but deal with it.
IK this is really bad. Just a tip, if you want to erase the whole thing, click the C key or click the flag. For more precise erasing, use the eraser button. If you want to take a screenshot of your painting, click the "S" key, and after you take your screenshot, click the "D" key.
