The Great Explorations in Math and Science (GEMS) project at The Lawrence Hall of Science developed a classroom activity, Color Analyzers, based on the Magic Cloth activity from our Colors From Space planetarium show. In that activity, students first use color filters to view color graphic images that have hidden messages embedded in them. It is when the students view the graphics through the red filter (Rosco #27, Medium Red) that the dramatic hidden messages suddenly appear.
Students then try to figure out how the hidden messages work—why certain colors seem to disappear when viewed through the red filter. They use crayons, colored penicls/pens, or computer graphics software to create their own images to test and experiment with.
Here are 11 images that are in the Color Analyzers teacher guide: