Rub random spots on the glazed surface of the pottery with a coarse, 40 grit and 60 grit, sanding block to remove the shine from these areas.
Sand over the areas you sanded with the coarse grit sanding block with a fine, 150 grit and 180 grit, sanding block to remove the deep scratches that the coarse grit sanding block left behind.
Place the pottery out in direct sunlight for one month and then turn it around so that the color fades on all sides. Leaving the pottery in a sunny window or greenhouse will work, but the sun, along with the weather elements will make the color will fade more quickly.