Mix the cake batter as directed on package.  Gently fold in the sprinkles just until combined so the colors stay. If you mix too much the colors will melt and mix into the batter making a solid brownish color. Pour into chosen baking pan and bake as directed on cake mix package. Let the cake cool and frost with your favorite frosting. If you have white frosting you can color it a fun color with food coloring.

When you cut into it, there are a bunch of tiny color dots and swirls...my kids love it!

Great for cupcakes too.