While feeling congested and miserable, this is what Jack did today.
We used double stick tape to attach a plain piece of paper inside a box. Next we chose three colors of paint and squirted a little of each onto the paper. Then we raided Ed's golf ball supply and put three of them inside the box. Finally we wrapped the box in cling film, just in case Jack felt tempted to reach in and pull out a golf ball.
Then he shook it up! This definitely took some encouragement.
I like the way the golf balls gave it a kind of speckely texture, but any kind of small ball would work.