DEW1.5. Dueling Beams of Light

The computer-based color explorations allow millions of colors to be viewed efficiently, but do you really believe it? Make and mix your own beams of colored light to see what happens.


  1. Two overhead projectors, or two slide projectors, or one of each
    If using overhead projectors, two sheets of thick paper or cardboard with cut out slightly smaller than filters If using slide projectors, two slide holders for filters 
  2. Filters
    Pack of color filters (at least 6 colors – red, green, blue, yellow, magenta, and cyan) from a distributor of science education materials. You may also order filters from lighting companies that sell colored gels for theater productions – see source of equipment.
ColorRosco Filter
RedDeep Salmon #42
GreenStandard Green #2004
BlueLight Sky Blue #67
YellowCalColor90 Cyan #4390
MagentaLight Straw #11
CyanCalcolor90 Magenta #4760
Courtesy of Bob Van Milligan who attended the MVH workshop in Portland, Maine during June, 2006.

Make your own filters using petri dishes, food color, and food dye.

What To Do

Red, blue, and green color circles with overlapping combinations

    Darken room.

    Turn on both projectors, put filters in place to color each beam, and merge beams.

    Challenge 1: Find two color filters in which the merged beams of filtered light produce yellow.

    Challenge 2: Stack these two colors over one beam of light (turn off second projector) and see what color is produced.

    Challenge 3: Find two color filters in which the merged beams of filtered light produce your favorite color.

    Challenge 4: Find two color filters that produce your favorite color by stacking the filters over one light beam.

Movies created by Marion Tomusiak, 
Museum of Science, Boston:

Mixing colors of light.
Filtering light.

Movies of mixing colors of light or…
Color basics in light and paint:

Mix Red, Green, and Blue (light or pigment)
Mix Red and Green
Mix Red and Blue
Mix Yellow and Blue

Mix Light Only

Movie of stacking filters over a light beam: