{R A I N B O W} Making FOOD fun! My friend Brooke is CRAZY creative! About a year ago I saw this cake on her blog, asked for the details. She dished. And now I am passing them on! Thanks BROOKE! (2) Boxes of White Cake Mix Sprite Zero And a WHOLE lotta food coloring (Follow the instructions on the back of the box, to get the colors you want!) Piled just so, a cup at a time, in a greased and floured pan.... Baked at 350 degrees for 28 min (or until it passes the "toothpick" test) and…