This is what you will need

Pour water into a container that you don't mind getting wrecked

Pour different colours of nail polish into the water.....

until you get something like this. I went for spots

Carefully place your object into the tin making sure you don't touch the bottom. Leave there for 5 seconds

Then slowly lift the object out of the water

This is what it may look like for you

Peal of excess nail polish

Leave it outside to dry for 2-3 minutes. If you want you can re-do the previous steps to cover all the other sides

This is the final product. There are many other things you can decorate using this method