Demonstration of the Spectrophotometric Complementary Color Wheel Using LEDs and Indicator Dyes

A quick, simple, and engaging demonstration of the spectrophotometric complementary color wheel is presented. Colored indicator dye solutions are illuminated under ambient room light and with different colors of light-emitting diodes (LEDs) in a dark room. The solutions are observed to be colored, black and opaque, or transparent and colorless in accordance with the color wheel, their optical absorption spectra, and the illumination conditions.