Remove the stones from the patio area if they are loose. You'll get the best results if you paint the entire stone, so unpainted sections will not be revealed if the stones shift positions in the future.
Wash the stones thoroughly. Use dish or hand soap and warm water. Use a scrub brush to get rid of dirt inside cracks and crevices; any dirt remaining on the rocks will keep the paint from adhering.
Dry the stones with a towel. If the stones are porous (such as sandstone or gravel), be sure to let them air-dry for several hours.
Apply a base coat. Use a white primer coat to even out the colors and texture of the stones. This will keep the varying colors in the stone from showing through your final paint job.
Apply a flat coat of color. Create any designs you like, or do a marble effect: paint a cover coat of a white, and let dry. Add a partial coat of gray using a kitchen sponge, then create a vein effect by dragging a feather through the top layer of wet paint.