The following is the vendors description of the demonstration.

The light output from the QED Color Mixer is produced by four separate ultra-bright RGB LEDs. Three slide potentiometers control each LED, allowing the red (R), green (G), and blue (B) light from each LED to be individually controlled and mixed as desired. Using these revolutionary RGB controls, the laws of additive color mixing can be demonstrated with unparalleled clarity and impact.

In addition, a set of filters can be placed over the LEDs to demonstrate subtractive color mixing. Six filters that pass either red, green, blue, cyan, magenta, or yellow can be placed over the LEDs ( set to emit white light) to demonstrate the principles of subtractive color mixing using filters. It is a simple matter to show the necessity of using secondary colors (cyan, magenta, and yellow) for subtractive mixing, like that used in inkjet printing.

The QED Color Mixer also has a unique feature found on no other color mixer. The special arrangement of the four RGB LEDs in the QED Color Mixer allow light to be passed through filters and mixed either additively or subtractively - at the flick of a switch! Change back and forth between the two modes, showing first the results of passing white light through each filter separately, and then mixing them additively on the screen. Then flip a switch to show the results of white light passing through all filters in turn, and the effect of subtractive mixing on the resulting colors. See the two pictures to the right for an example done using cyan, magenta, and yellow filters.