In this lesson, students explore the visible light spectrum using a flashlight and red, blue and green theatrical gels or cellophane. They also record data on a worksheet, and learn about mixing wavelengths of light. A student worksheet, data sheet, answer key, assessment, and Web links are included. This is Lesson 1 in Understanding Light, part of IMAGERS, Interactive Media Adventures for Grade School Education using Remote Sensing. The website provides hands-on activities in the classroom supporting the science content in two interactive media books, The Adventure of Echo the Bat and The Adventures of Amelia the Pigeon.