Adjust the sliders to change the color. You can see the selected color in the circle. press clear the erase your whole drawing. you can also change the size with one of the sliders.
credit to this video: https://www.youtube.com/watch?v=9J44i3Xh2HQ i used it to help me. if you want to erase just get black color by turning brightness down all the way. Have fun!