PASCO COLOR MIXER
This it the easiest and most effective way I have found to demonstrate light mixing. The PASCO Color Mixer allows students to play with how light mixes by adjusting the intensity of the red, green and blue LEDs. Exploring additive color mixing is as simple as using any flat surface to project the light upon. The optional Color Mixer Accessory Set works best for older students. It contains 7 colored filter cards and 11 colored reflector cards for study of light color transmission and reflection.
Note: Teachers/schools will need to have an account with Pasco to purchase.