Gradient Rainbow Buttercream Cake Tutorial

rainbow buttercream cake by sugar and sparrow

If you’ve been following along on my Instagram, you know that I’ve been completely nerding out on my Americolor Nifty Fifty Kit. Having 50 beautiful food color gels in my collection has been a complete game changer when it comes to coloring buttercream (and all the edible things!) and I’ve gotten to create some really cool, colorful cakes since getting the kit. You can see a few of the cakes I’ve created, real life color swatches, and read more about the kit in this post, but today I want to talk about this gradient rainbow cake. Can you believe it features 20 different colors from the Nifty Fifty Kit? I am in love.

I’ll walk you through the step by step below. First, here’s a quick video tutorial of how I created this gradient rainbow cake, from mixing the colors to applying them:

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You Will Need:

  • A cake that’s been frosted and chilled
  • 1.5 batches of vanilla or other light colored buttercream
  • Food color gels in rainbow shades. I used colors from The Nifty Fifty Kit (detailed below)
  • Plates and spoons for color mixing
  • Piping bags
  • Scissors
  • Ruler

Step 1: Mix Up Your Colors

Divide equal amounts of buttercream across a few plates or in separate mixing bowls. Like I said before, I got a little crazy and mixed up 20 different shades from my Nifty Fifty Kit. The colors I used (in rainbow order) are: Watermelon, Burgundy, Super Red, Soft Pint, Deep Pink, Orange, Peach, Electric Orange, Electric Yellow, Lemon Yellow, Egg Yellow, Electric Green, Leaf Green, Forest Green, Teal, Sky Blue, Navy Blue, Electric Purple, Regal Purple, and Eggplant.

rainbow buttercream

The important thing with these colors is that you have a few different shades of each rainbow color, whether you use the same color in different intensities or more varied colors for each of the seven rainbow hues.

Step 2: Fill Your Piping Bags

Prepare several piping bags (enough for each shade you’ve created) by snipping off a ¼ inch opening off the tip with your scissors, then filling each bag with a different shade. It helps to have disposable piping bags for this step.

rainbow buttercream by sugar and sparrow

Once you’ve got your bags all filled, line them up in the order you want to pipe color-wise. Look at all those piping bags! I was swooning before I even started adding the colors to the cake.

Step 3: Measure Out Sections On The Cake

Using a ruler as your guide, mark off six equal sections with an icing spatula or other sharp object. It’s important that you start with a cake that’s been frosted and chilled so your marks are sharp and unwavering. Place marks horizontally all around the cake so you know where each color should end and a new one should begin. This way, you’ll have nice equal sections of color instead of getting towards the top of the cake and realizing you barely have room for the last few colors.

measure equal sections on a cake

Note that you’ve marked six equal horizontal sections but have seven colors. This is because the top of the cake will act as its own (seventh) section.

Step 4: Apply The Colors

Now for the fun part! Starting at the bottom of the cake, pipe the purple hues within the bottom section you’ve marked off. I chose to start at the very bottom with the darker purples (Eggplant and Regal Purple) and saved the lighter purple (Electric Purple) for the top of the section. There’s no real pattern here other than that. The cake ends up looking really cool with the dots in a more random order rather than piping lines of the same color. In other words, it’s ok to have some of the darker purples toward the top of the section and put different colored dots next to each other.

how to pipe dots onto cake

Pipe a few stray purple dots into the section that should be blue to help with the gradient effect, then fill the rest of the next section in with the blue hues. Again, I’ve chosen to pipe the darker blue (Navy Blue) toward the bottom of the blue section and the lighter blues (Sky Blue and Teal) toward the top.

piping dots onto cake

Repeat this process in reverse rainbow color order with the rest of your shades. When you get to the top of the cake, pipe all of the red shades. Remember to pipe a few stray red and pink dots down into the orange section to help with the gradient effect.

colorful cake by sugar and sparrow

how to make a rainbow cake

How cool is this gradient rainbow buttercream cake? I absolutely love color and having my Nifty Fifty Kit made all of my colorful cake dreams come true with this one! It’s well worth having the entire kit in your cake decorating collection. These gels last for ages and save tons of time you would have otherwise spent custom mixing different color gels to get just the right shade. Let me know if you end up making this cake and/or getting the Nifty Fifty Kit! I would love to nerd out on color with you.


  1. Nina Fattahi

    How many layers is this cake? In other words, how high do I have to make it? I’m making this for my daughter’s first birthday smash cake!

    • Hi Nina! This cake was three 6 inch layers and ended up being a little over five inches tall. The design will work for any size cake though! Whatever height you end up with, just divide it into five equal sections and follow the tutorial. Good luck and happy birthday to your girl!

  2. Wow! I just made this gorgeous design today! Took a loooong time, but I think it looks pretty, but not as pretty as yours, Whitney! Thank you, as always, for such amazing inspiration. I will take a couple of pics and tag you so you can see! 🙂

    • Yay, Paula! Haha yes, this design definitely takes patience but so worth it. I can’t wait to see how yours turned out!!

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