At my house, we are always looking for that magical body paint recipe. We've had a few misses, but have found several good ones. We discovered this one by accident.
This started as a shaving cream activity. Bobo asked to add paint to make "Hulk's blood," which just means green. We added yellow and blue powder tempera paint. It turned the shaving cream green, leading to shedding all clothes, leading to painting the body, leading to sitting in the mixture. "Mama, my booty's green."