T.B.
You could also let a cake tell the story. Just follow the instructions on a plain white box cake. Divide the batter in 1/2, add a bit of blue food coloring to one bowl and pink to the other. Pour each batter bowl into their own round pan and bake. Viola you now have a pink and blue layer cake when done. Frost as you normally would. Then have the grandparents over for dessert :)
Good Luck and God Bless!