Paint your image using watercolors. You'll need to get your brush loaded with paint and water since the plaster soaks up the liquid. Also, start with the lightest colors you want to paint, say, yellow, and work your way down the line towards black. You can always go darker, but you can't lighten up watercolors on plaster.Make sure you add details and a ground and sky, if applicable. I encouraged the students to paint right off the edge of their pieces (on the 1/2" side of the plaster piece).