Rainbow Test Tubes Activity


Problem: How many colors can be created by starting with red, yellow, and blue solutions?


Updated Jan. 10, 2017 with results:

Results 2016-17

Materials per group of 3-4 students:

  • Student Handout RainbowTestTubesPublic (pdf)
  • Spreadsheet to collect data (excel – public)
  • 9-10 test tubes with test tube rack
  • Erlenmeyer flasks filled with red, yellow, and blue solutions of food coloring and water
    • 5 drops of food coloring per 200 mL (25 per 1L)
  • 3 x 25 mL Graduated Cylinders
  • 3 x 10 mL Graduated Cylinders
  • pipette
  • beaker filled with clean water
  • large beaker for used water
  • this activity took 2x 50 minute class periods


This lab is an updated version of the classic Rainbow Lab (link) that has been around since the 80’s (Measuring Liquid Volume with a Graduated Cylinder 1988). I used this for many years with my 5th graders, and previously with my 6th graders in the early 2000’s. Now that I am teaching 6th grade again, I wanted to make it more open ended and challenging. The purpose of the original version of the lab was twofold: First – could they follow directions carefully to make a rainbow? Second – how precisely can they measure liquid volume?


For the new version of this lab, I created new objectives and assessed the students based on their problem solving, collaboration, and measuring skills.


  • Students will be able to precisely measure liquids with a graduated cylinder
  • Students will be able to create their own lab procedures using the given parameters to guide them
  • Students will create new mixtures and solutions
  • Students will be able to record accurate data
  • Students will collaborate and problem solve to achieve a common goal
  • Students will test, evaluate, and select the best proportions to create the colors orange, green, and purple
    • each group made 3-4 different combinations for each color and had to, as a group, determine which combinations of primary colors created the best secondary colors
  • Students will follow proper lab procedures to avoid color contamination
  • Students will record and analyze data from the whole grade and compare their findings to the averages from each group, what patterns or trends did they notice in the data?
  • Students will create their own ‘designer’ color and share it with the class
    • this was fun way to wrap up the activity, we had a ‘fashion’ show with each group coming up to the front of the room to showcase their newly created and named colors
    • if time allowed, at the end we made a rainbow with each student holding their test tube and standing next to a person who had a color similar to their own, from Red to Purple
Visual assessment – all test tubes are even and you can quickly see that each color has a volume of 25mL.