Use the circle cutter to cut a 2-inch-diameter circle in the center of a cardboard square and a 3-inch circle in the center of the second cardboard square. Remove the circles (you'll use the squares as stencils).
In a well-ventilated work area, cover the work surface with newspapers. Pull the ornament apart and spray-paint the outside of each half white; let dry.
On the outside of one half of the ornament, place the 3-inch cardboard circle stencil over the rounded center. Spray-paint the visible ornament circle green; let dry.
Lightly mist the outside of the green circle with black paint; let dry. Remove the 3-inch circle stencil.
Center the 2-inch circle pattern on the green circle. Spray-paint the visible ornament circle black; let dry. Remove the 2-inch circle stencil.
Fill the ornament with Halloween candy and press the halves together.