Marbled Pumpkin - Painted Pumpkins - 26 Easy Projects to Perk Up Your Halloween - Bob Vila
Fill a bucket (one you don't mind getting a little paint on) with water. Then pour in the contents of three bottles of nail polish. With a stick or skewer, swirl around the paint, which is now floating at the top of the water, to make a design. Dip your pumpkin in sideways and submerge it. While holding it underwater with one hand, use the other to soak up the rest of the nail polish with a paper towel. Remove the pumpkin from the now clean water, let dry, and there you have it!