Back in the day the street kids would sell rocks at the corner instead of lemonade. We’d paint them to suit their shape and texture to make it look like something (usually an animal or so). But our first summer we used watercolors. We sold one to a lady that lived on our block. After a few days we noticed her rock was already fading so while she was out we stole her rock and repainted it. You wouldn’t believe how many people bought these things for a couple of quarters.