This can be a project all of its own, or can be used in connection with the slides. Have students cut glasses frames from posterboard. Real sunglasses can be used for templates. Frames can be elaborately decorated before colored cellophane is taped in for lenses. Students can experiment with all sorts of combinations of colors, although the traditional red and blue lenses have the greatest 3-D effect.
Students can then view their watercolor paintings using their own glasses.
Arrange the cellophane directly on the glass, so that colors overlap and create a collage. Colors behave somewhat differently when mixed on a computer. That is because light is being mixed instead of pigments. Show students this difference by printing a color copy of their digitized design. Compare the printed image with the one on the screen.