I totally copied this idea from I Heart Crafty Things, but she found it here. We started this project yesterday. I squirted yellow and red paint on each child's white piece of paper and they mixed it up and painted the whole thing.
Today we did all the cutting and gluing. The kids in my class are 4 and 5 so they have trouble cutting circles and ovals free-hand. I had them flip over their paper and draw their pumpkin on the back. Then they cut it out.