First you are going to make the cake dough as in the instructions of the back.
After you finish the cake dough you are going to separate into different bowls to add the artificial food coloring
I do not use exactly the colors of the rainbow I use yellow, red, blue, green and orange. For all I started to add the colorant slowly until I like the color. And for the orange I use yellow and red.
May look more or less like this.
Now in your cupcake pan you are going to place the dough in the order that you like the colors adding about one and a half tablespoon of dough.
Once you start adding the second layer of dough you should always do from the center only, slowly pulling up the ends without mix. Also remember to fill out a little more than a half the cupcake pan.
When you finish you are going to bake them in your preheated oven approx 15-20 minutes at 350. This varies depending of the oven so take a toothpick and when it comes out clean it will be ready.
When they are ready take them out carefully to cool down.
Once cold they are ready to eat! I do not get frosting but if you like you can put them. The inside will look like this, you can also make cake like this and it looks very cute, I hopeyou like it!