St. Patrick’s Day Fun in the Blog~ Rainbow Filling Tutorial!

Hi everyone! Today I’m going to share a fun trick for adding “rainbows” to the inside of your cakes, and just in time for St. Patrick’s Day! ;0) –

Instead of tinting cake batter for a colorful cake, today’s tutorial focuses on adding a little flair BETWEEN your layers. It’s a quick, easy, and fun technique to have in your decorating bag of tricks!


I started with three 8 inch chocolate cake layers, and about 1 cup of VANILLA BUTTERCREAM for each color.  (Looking back, 1/2 cup of each color would have worked fine..I had leftovers!) –

Here are the coloring gel colors that I used:  Americolor Super Red, Orange, Lemon Yellow, Electric Green, Sky Blue, and Regal Purple.

I filled my disposable piping bags with my tinted buttercream, and snipped off the tips.


Starting with the red, I piped a circle (approx 1 inch wide) in the center of my bottom layer of cake.  I used toothpicks to mark off where my remaining colors would fall, allowing for about 1/2 inch for each color.  Adjust as needed depending on the size of your cake (mine is 8″).


Moving right along… I encircled the red spot of frosting with orange, then yellow, green and so on.


Next, I placed my next layer of cake on top of our colorful bullseye pattern, and repeated once again for another colorful layer of filling.



I placed our final layer of cake on top and frosted the cake with vanilla buttercream.


Then, I added a few shamrocks!  Using buttercream tinted Mint Green, I piped heart shapes into a shamrock pattern using a Wilton tip 2.



I piped several more! (Some are a little larger, piped with a tip 5).


I added a few more dots of color to the outside and a small green bead border.


Then, slice to reveal your rainbow!


I hope that you enjoyed this little tutorial, have a great weekend!!!

Category: Blog Tutorials, Buttercream Techniques, Spring


  1. Paula M. says: #1

    Fun idea Melissa!! So clever and eye catching.

  2. Sally Loda says: #2

    Wish I had seen this yesterday! 😉 I would have loved to do it for my cake.

  3. abha says: #3

    Thanks a lot. I really loved it

  4. MsGF says: #4

    Love it! Very clever.

  5. Carol says: #5

    I like it! And gives a new meaning to taste the rainbow. LOL

  6. Joy says: #6

    Love this tutorial. It’s so festive and cute!! Thank you for all of your great work!

  7. Melissa Diamond says: #7

    Thank you for your comments!!

  8. scott says: #8

    Oh great! I now know what to bake For St. Patrick’s Day !

    I have been so busy : ) I have missed all of you.


  9. Mary says: #9

    That is so cool! You have such creative ideas!

  10. Dina says: #10

    Awesome Idea, I will have to do this for St patty’s day :)

  11. mandy says: #11

    Looks awesome

  12. trisha says: #12

    I am just KICKING myself for missing this for Sophia’s bday (she was born on 3/17) Aggggggghhhh!! This is awesome! Love catching up here today…..smiles everywhere along w/ good inspiration.

  13. Melissa Diamond says: #13

    Thanks for all of your comments!! @Scott~ We’ve missed you too! ;0) –

    @Trisha~ So happy to see you here, how much fun that Sophia’s b-day is St. Patrick’s Day ;0) – You will have to plan a rainbow sneak attack for her in your next cake, just for the fun of it! xoxo

  14. María José A.G. says: #14

    sencillamente deliciosa, además colorida como a mi me gustan.

  15. komal says: #15

    Very beautiful
    It seems hard but ur tutorials make it so easy
    I will try it
    My son’s b day

  16. Ansa Hogan says: #16

    LOVE this cute idea!

  17. Melissa Diamond says: #17

    Thanks Ansa!! xo

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