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Mix and Match


Required Materials


  • Mix and Match colors with Light1 piece of white paper

  • 4 clear plastic cups

  • Red, yellow, green and blue food coloring

  • Pencil

  • Flashlight

  • Newspaper

  • 4 cotton swabs

  • Water

  • Ruler

Activity Directions


  1. Cover your workspace with newspaper.
  2. Place a few drops of red food coloring on one end of a cotton swab.
  3. Using the swab, make a dark red dot about 2 cm in diameter on the white paper. Repeat this process with each of the remaining 3 colors.
  4. Fill each cup halfway with water.
  5. Add 3–5 drops of food coloring to each cup (a different color in each cup), and mix with a matching swab.
  6. Turn on the flashlight and darken the room.
  7. Hold the cup of red water directly above the red dot.
  8. Shine the flashlight straight down into the cup of red water and look at the red dot. What color do you see? Record your results in the chart.
  9. Repeat the process until you have tried all the water colors with all the colored dots. The data chart will help you keep track of the combinations you tested.
    • Water Color Dot Color Color You See
      Red Red  
      Red Blue  
      Red Yellow  
      Red Green  
      Blue Red  
      Blue Blue  
      Blue Yellow  
      Blue Green  
      Yellow Red  
      Yellow Blue  
      Yellow Yellow  
      Yellow Green  
      Green Red  
      Green Blue  
      Green Yellow  
      Green Green  
  10. What did you discover about mixing color and light? Does it make a difference if you set the cup down or hold it above the dot? Do you get the same result for blue if you make really dark blue water?
  11. You’ve just mixed different wavelengths together. When you are looking into the red water as it is held above a yellow dot, you see two wavelengths at the same time. The wavelength for red and yellow combine and you see orange.
  12. Visible light contains ROY G BIV, with three of the seven colors considered primary: red, yellow, and blue. Primary colors can be combined to make the other colors of the rainbow. Red + yellow = orange. Look at where orange is in ROY. Now what colors make green? Is the order of colors in a rainbow a coincidence?

Want to mix colors online? Visit these cool websites:

Project Lite: Addition Photo
Project Lite: Einstein

Here's What's Happening


To find this experiment and many more please download the Lighten Up! Discovering the Science of Light book, developed through a partnership with the Optical Society of America’s Foundation (OSAF) and the Girl Scouts of the USA.

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