Preheat oven to 350°F.
Spray bottom of 13x9-inch pan with cooking spray.
In large bowl, beat cake mix, water, oil and eggs with electric mixer or hand mizer on low speed 30 seconds.
Beat on medium speed 2 minutes, scraping bowl occasionally. Pour into pan.
Bake 28 to 32 minutes or until toothpick inserted in center comes out clean.
Cool on cooling rack 20 minutes.
After cake has cooled, poke cake every inch with a chopstick or wooden spoon handle
Once cake has cooled, in a medium bowl, pour 1 cup boiling water on strawberry jello.
Stir until gelatin is dissolved. Add ½ cup of cold water and stir.
In a separate bowl, mix blue jello with 1 cup of boiling water and stir until dissolved.
Add ½ cup of cold water and stir.
Start with one color jello and carefully pour strawberry gelatin into alternate holes with a small spoon,
Then repeat the process with the 2nd color jello and pour into empty holes.
Cool in refrigerator completely, about 1 hour.
Frost with whipped topping.