I finally did it!
after several hours and a very messy kitchen.
I managed to produce a semi-decent rainbow layer cake.
Here is how I did it!
1 box of white cake mix prepared according to the directions.
A variety of food coloring colors....I chose to use the wilton gels because I read somewhere that they work better because they dont add moisture to the cake.
Divide the cake in to equal parts depending on how many colors you plan on using. To make this easier I used a measuring bowl. Since I they knew how much batter I had it was much easier to divide it up.
Once the batter is divided add the colors. I had to play with the amount of coloring I put in to get the right colors.
Bake each color individually. I cut the bake time in half for each pan because there was such a small amount of batter in each pan. Once the cake has completely cooled remove the cake from the pan. I mean completely cooled. I ran into some issues with my cakes being too moist and warm. Even after you remove it from the pan let it sit before you level the layer. Once you have done this too all of the layers build your cake! I suggest doing a crumb coat first and then icing the cake. Unfortunately I do not have any advice for that portion because I did not do a very nice job of icing the cake.
Hereis a simple frosting recipe.
Hopefully I can make another one soon and improve on the look of it!