Prepare cake as directed on box and add small chocolate chips and red food coloring to the batch before baking . Use 13x9 inch pan. Once cakes are done cooking, place the cakes in freezer. The cake will be a lot easier to shave/shape and frost frozen. Once frozen, stack the cakes on top of each other adding the red colored frosting in between cakes. (Add red food coloring to a small amount of the white to use in between the cakes when stacking them.) Shape your cake with a butter knife by shaving it until it resembles a watermelon shape.

Prepare frosting by adding the green food coloring to 2 of the containers. You will need to save a little bit to make it a darker green to make the stripes on the rind. Leave some white frosting to frost the outside of the cake first. (This is the white part of the rind). So after your cake is shaped, frost it with the white frosting first, you don't need a whole lot. Then frost over the white with the green. Use the darker green to add the stripes.