My family likes going to our local Boardwalk (dining and shopping along the lake) for dinner on Friday nights because they have live music and an open space. The kids love to run around in the green space and dance to the music. A few weeks ago they had a wonderful children’s singer and it was so awesome for the kids! 

One of his songs was about the colors of the rainbow. The musician sang and the kids yelled with him all the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. Ok, I think it’s been way too long since I have been in elementary school because they lost me after blue. I was singing along and went from blue to purple….I didn’t know (or remember) indigo and violet.  This performer’s cute song left me wanting to learn more about rainbows. 

Let’s talk about Rainbows:

I have since confirmed that, yes indeed, there are 7 colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. The rainbow color sequence is attributed to none other than every engineering student’s favorite physicist: Sir Isaac Newton. He did extensive research into color, light and optics and in his book Opticks named the 7 colors of the visible spectrum of the rainbow. The rainbow colors always appear in the same order of red, orange, yellow, green, blue, indigo, and violet from top to bottom. 

To view a rainbow you need three conditions to align: your back is to the sun, the sun is approximately 40° from the ground, and there are suspended droplets of water or a light mist (rain, mist from a waterfall, or even backyard sprinklers). The individual droplets act as tiny prisms that reflect, refract (or bend), and disperse light into the circular spectrum we see as a rainbow. 

The concept of how rainbows form is quite complex and requires a deep understanding of optics, which I won’t get into here on my blog. If you want more detailed information on rainbow formation beyond what I’ve briefly shared here, I recommend you start with Wikipedia’s entry on Rainbows and also the Physic Classroom’s page on Rainbow Formation. 

Today I’m sharing two outdoor and two indoor Rainbow-themed experiments for kids. The first experiment is finding the right conditions to view a rainbow outdoors on a rainy day. The second is about finding rainbows in sprinkler spray. The third experiment is making an indoor rainbow using a glass of water. The fourth experiment is a foaming rainbow color reveal using baking soda and vinegar. In these experiments we’re introducing our kids to meteorology (if you’re viewing rainbows on a rainy day), physics (refraction and optics and their role in the formation of rainbows), chemical reactions (baking soda and vinegar), and learning and practicing identifying colors.


Outdoor: Rainy Day Rainbow Viewing Experiment

In this experiment you’ll seek out the perfect conditions to view a rainbow on a rainy day. This experiment is appropriate for children of all ages. 


The weather is the main safety risk with this experiment. I do not recommend standing outside to look for rainbows if there is lightning and thunder nearby. Also, if it is raining heavily, be sure to dress appropriately for the conditions (umbrella, rain boots, and rain jackets) to keep kids comfortable and dry. 

Materials needed:

  • Rainy day
  • Towel to dry off after standing in the rain (optional)


Patiently wait for the perfect rainy day for viewing a rainbow. Here are the ideal conditions for observing a natural rainbow: 

  1. A rainstorm, but the sun is visible to the East in the morning, or West in the evening
    • For a morning storm, the rainbow will be observed in the Western sky (with the sun in the East facing your back)
    • For an evening storm, the rainbow will be observed in the Eastern sky (with the sun in the West facing your back)
  2. The sun needs to be at a 40° angle from the ground (this would occur close to sunrise or sunset), see diagram below for reference on the ideal sun position.
  3. Once you find a day with these perfect conditions, go out with your family to find the rainbow and enjoy the beautiful meteorological phenomena. 

Ask your children to do these things to “learn” while observing the rainbow:

  1. Identify all the colors they see in the rainbow from top to bottom – learning colors 
  2. Follow the arc of the rainbow with their fingers (explain that it makes a half circle) – learning geometry
  3. Guess where the rainbow begins and ends  learning geography
  4. Catch a raindrop with their tongue, explain to your child that rain is evaporated water from the ocean. – learning meteorology 

What happened:

You were able to observe a rainbow because the three required conditions aligned (sun at your back, sun is 40° from the ground, and it’s raining). Rain can happen frequently, or infrequently, depending on where you live, but you don’t see a rainbow every time it rains. 

Sometimes the sun is not visible because there are too many rain clouds. Sometimes the time of day it rains isn’t right and the sun is too high or too low in the sky. When the conditions are right, a rainbow can be magical to observe with children. 


Outdoor: Backyard Sprinkler Rainbow Experiment

In this experiment the kids get to play and cool off in the backyard sprinklers while they learn about how rainbows form. This experiment is fun for kids of all ages! My almost 4-year-old and 19-month-old both loved this experiment. 


On a hot and sunny day, be sure the kids are covered in sun protection clothing and/or sunscreen. Even 5 minutes in harmful UV direct sunlight can cause irreversible skin damage in young children. 

Materials needed: 

  • Sprinkler
  • Sunny day
  • Sunscreen (optional)
  • Towels to dry off after playing in the sprinklers (optional)


  1. Turn on the sprinklers
  2. Stand near the sprinklers with your back to the sun
  3. Look for a rainbow in the spray (it should be at a 40° angle from the ground, so look down slightly towards the shadow of your head)
  4. Move around and notice that the rainbow moves too! Each person will see their own unique rainbow. 
  5. Ask your child to identify all the colors they see in the rainbow
My kids may or may not have found rainbows in the sprinklers, but they sure did have fun playing in the sprinklers outside on a hot summer day!

What happened:

The sunlight shined through the water drops in the sprinkler spray and refracted the light to create the rainbow. 


Indoor: Water Glass Rainbow Experiment

In this experiment you’ll see a rainbow form as the light refracts though your glass of water. This experiment is great for preschool age children (ages 4+) who can safely hold a glass of water without spilling water or dropping the glass. Younger children (like my 19 month old toddler) will enjoy observing this experiment. 


Make sure you are supervising your child while holding the breakable glass. Glass easily shatters when dropped so use caution when doing this experiment, and if the glass drops and breaks, first remove the children from the room, then return alone to safely clean up the broken glass shards. 

If water spills, mop it up immediately to prevent a slip hazard. I have left spilled water thinking I’ll clean it later only to forget and end up slipping on it! 

Materials needed:

  • Glass
  • Water
  • Window with bright direct sunlight
  • White paper (optional)


  1. Fill the glass with water
  2. Bring all materials in front of a window with bright, direct sunlight
  3. With your back to the window, hold the glass of water above the white paper or in front of a light colored wall
  4. Adjust the height and angle of the glass of water until a rainbow appears on the white paper or wall below. 
  5. Ask your child to identify all the colors of the rainbow they see appear on the paper or wall

What happened: 

When the sunlight passes through the glass at the right angle (40°), the water makes it refract to form a rainbow on the white paper or wall below. 


Indoor: Baking Soda & Vinegar Rainbow Color Reveal Experiment

Note: This post contains affiliate links. You may read my disclosure here.

As you know from my 3 Valentine’s Day themed Baking Soda and Vinegar Experiments for toddlers post, we love baking soda and vinegar experiments! Basically every time I tell my son we’re doing a science experiments, this is what he’s expecting. While he did like the other rainbow experiments we did in this post, after the third one he told me, “I want to wear my glasses and squirt vinegar into a cup.” How can I say no to that?! 

So I tied it in to our rainbow theme by doing a rainbow color reveal! In this experiment we’ll hide food coloring under baking soda, then use a squirt bottle to pour vinegar over to real the color in a bubbly chemical reaction. This experiment is great for toddlers (ages 18 months+) who are capable of squeezing a bottle with control on their own.


A chemical reaction occurs in the following experiments which creates carbon dioxide bubbles. There is very small chance that the bubbles can rise out of the dish and if you are watching too closely can splash into your eyes. If this happens, immediately flush the eyes with water until they are no longer irritated.

To prevent this unlikely event from happening, don’t observe the reaction too closely, and/or wear eye protection. I highly recommend these safety glasses that my kids and I use and they fit the kids well!

Food coloring can stain clothing, furniture, and skin. Before using food coloring, it’s a good idea to protect your work surfaces by covering them with newspapers or paper towels and wear clothes you don’t mind getting stained. It’s always a good idea to read the labels on the food coloring and choose a brand that has ingredients you are comfortable with using in your home.

Materials needed:

  • Baking soda
  • Vinegar
  • 7 small clear bowls
  • Food coloring (red, yellow, green, and blue)
  • Small squeeze bottle
  • Safety glasses (optional)


(Tip: Do steps 1-4 without your children present so the colors are a surprise!)

  1. We’re going to make the 7 colors of the rainbow, one in each small clear bowl
    • For Red: use 4 drops of red food coloring
    • For Orange: use 3 drops of red and 3 drops of yellow food coloring
    • For Yellow: use 4 drops of yellow food coloring
    • For Green: use 4 drops of green food coloring
    • For Blue: use 4 drops of blue and 1 drop of green food coloring
    • For Indigo: use 4 drops of blue food coloring
    • For Violet: use 3 drops of red and 2 drops of blue food coloring
  2. Cover the food coloring in each of the 7 bowls with a thin layer of baking soda (about 2-3 tablespoons per dish).
  3. Fill the squeeze bottle with white vinegar
  4. Arrange the 7 small bowls in rainbow order on a table in front of your child
  5. Let your child slowly squeeze the vinegar into each bowl, the color will be revealed along with foam!
  6. Ask your child to identify each color as it is revealed.

What happened: 

When the vinegar was poured onto the baking soda the chemical reaction immediately began. Carbon dioxide gas was released creating the foam. As the foam created by the chemical reaction dissipated, the hidden color was revealed. For more details about the science behind the baking soda and vinegar reaction, please see my Baking Soda Experiments for toddlers post.

I hope you enjoyed learning about rainbows with your children as much as I did! Now I can happily sing along with the children’s songs about rainbows knowing all about the 7 colors: red, orange, yellow, green, blue, indigo, and violet. 😉

Let me know if these tips helped you have success during your next rainbow hunt! 🙂


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