For Boo's birthday, she wanted a cake that was "kind of like" Bug's rainbow cake, "but with different colors and it should look different."
So, I used 2 boxes of white cake mix, 4 gel colors (rose, burgandy, cornflower blue and lavender), my Pampered Chef checkerboard cake pan insert (I couldn't find it on the Pampered Chef site so here is the Wilton version if you want to see it), Tropical Fusion Jello and a large tub of cool whip to make this cake.
I didn't take photos of the prep process but I put the insert into cake pan #1
and filled the outer ring and inner ring with 1/2 blue and 1/2 lavendar batter, then swirled the two together with a knife. Then I poured the rose and burgandy batters into the middle ring and swirled that together. Repeat this process in pan #3.In pan #2, reverse the colors so that the middle ring color from pans 1&3 becomes the center and outer rings in pan 2. Once baked, you stack pan #1, then pan #2 then pan #3. Frost lightly between layers.
For frosting, I used jello to flavor and slightly color cool whip. I swear I saw a recipe that told you how to make this but when I started looking for it yesterday, all I could find were recipes using Jello PUDDING and cool whip. So, I sort of struck out on my own. I used a 32 oz tub of cool whip (you probably don't need this much!) and a 3 oz box of jello. Mix the jello with 1/2 cup of boiling water. Stir and let powder dissolve for about 2 minutes. Add about 1/3 cup of ice. Gently fold into softened cool whip. Refridgerate for about 20 minutes and then frost the cake. After frosting, I suggest you cool the entire cake for about an hour to set the frosting. Be sure to refrigerate your leftover cake as well.
Results were a bit lopsided but I was in a bit of a hurry. The colors should be squares and lined up with each other. Somehow mine ended up tilted and artsy. That suited Boo just fine. The frosting got some rave reviews so I must have done something right! I have plenty frozen in the freezer for whatever cake comes along next :)
Boil 1 cup water in a pot on the stove. (While you wait for the water to boil, lightly grease the bottom of a 9x13 cassarole dish.) Stir in blue jello to boiling water. Bring to a boil again, then remove from heat. Add gelatin mixture and 1/2 cup cold water. Pour mixture into cassarole dish and put in refrigerator. 
