I made this cake from scratch, but you can use a white cake mix from a box if you want it to be really easy. I baked mine for 25 minutes, but it really depends on your oven. You can also make this in a 9"x13" pan or as cupcakes.
Preheat oven to 350 degrees. Grease cake pans or line with parchment paper.
Cream together butter and sugar. Beat in eggs, one at a time. Stir in vanilla and milk.
In separate bowl, combine flour and baking powder. Sift or whisk together. Slowly add flour mixture to butter/sugar mixture. Stir until well combined.
Separate batter into 5 or 6 different bowls. Add food coloring with different colors. Stir well.
Starting with one color, pour equal amounts into each cake pan. Do this for each color, but do not mix the batter once in the pans.
Bake for 25 to 40 minutes, depending on your oven. Check frequently towards the end to make sure you don't over bake. Check with a toothpick, if it comes out clean, it is done. The cake will spring back up when touched on top.