I tried out a new technique in kindergarten and first grade this year. We were using diffusion to create paint from washable markers. After viewing the works of Kandinsky, we used Sharpie markers to trace circles and rulers for straight lines. Then we outlined those with primary colored washable markers. After the lines had color, we used wet paintbrushes to spread the colors.
They loved the magic of water and markers and we got an introduction to color mixing when the colors overlapped.