I see my grandchildren frequently while Meg and I hang out. On this occasion, I was set up to babysit all day, so I tried to have nice activities for them to do. They, like most kids, love to paint. We have little items that we keep with the paints that can be painted over and over again, like ceramic figures and rocks.
We also have carved wooden figures, a squirrel and a large duck which they had the pleasure of painting. When those dried, they were tucked away to be painted with a different color next time. It is the process, not the finished product that matters here!