While we are pretty sure the inspiration for this project came from Teach Preschool, I couldn't find the exact activity so in order to give credit where credit is due, I'll link you up with Deborah's sensory bags.
Guada set up this activity with the kids. She prepped the bag by using a sharpie to draw fall leaves, pumpkins, or turkeys on the outside. She then offered the children spoons and babyfood jars of paints in fall colors. It was fun to watch the colors combine and sometimes and mix together into a nice autumn brown, and other times just swirl for a marbled effect.
Here it looks like somebody had a system for getting himself an orange pumpkin!
In the link above, Deborah informs us that a little nail polish remover will take the white "ziplock" label right off of the baggie. Useful knowledge for us preschool teachers!