RGB Light Mixer

In this simulation a red, a green and a blue spotlight shine on a wall. Students drag each lamp across the wall and watch the light add together: red and green make yellow, green and blue make cyan, red and blue make magenta, and all three make white. Clicking a lamp turns it off or on. Moving the pointer over the wall shows the hex code, the RGB values and the name of the mix at that spot. Sliders change spot size and brightness, and buttons overlap all three lamps or pull them apart. It teaches additive color mixing and how screens and stage lights work, and contrasts it with mixing paint.

• Drag the red lamp onto the green lamp and read the Mix readout where they overlap.
• Press Overlap all and check that the center turns white with RGB near 255, 255, 255.
• Click one lamp to turn it off and see which color is left where the other two overlap.
• Lower Brightness and Spot size and read how the RGB values change.
• Move the pointer over different parts of the wall to read the color there, then press Pull apart.

1. 1Predict the color made when two colored lights overlap.
2. 2Explain why red, green and blue light together make white.
3. 3Read RGB values and hex codes for a mixed color.
4. 4Contrast additive light mixing with mixing paint.

Questions teachers ask