Watercolor Works Fold a 9" x 4 1/2" piece of paper in half, and trace a faint pencil grid onto the front. Set up watercolor paints, and instruct your kid to paint the squares in different shades. Let dry. Then use a toilet-paper tube bent into a heart to stamp acrylic-paint hearts onto the watercolored cards. To swap colors, cut off the end for a clean stamp.