How to Change Color of Pennies or other copper objects: 1/4 c white vinegar, 1 tsp salt, A clear, shallow bowl (not metal), Paper Towels. Mix salt vinegar in bowl. Stir til salt dissolves. Add pennies. After 5 min, take out half of pennies; Put on paper towel. Remove rest of pennies. Rinse them really well under running water, put on a paper towel. In abt 1 hour rinsed pennies will look shiny and unrinsed pennies will be coated with a blue-green compound called malachite.