Preheat the oven to 350˚F. For the first layer, mix together the Funfetti cake mix, egg, oil, and aqua food coloring. Press into a foil-lined, greased, 9×9″ pan. Bake at 350˚F for 10-12 minutes.
Remove the cake mix layer from the oven and put spoonfuls of the marshmallow cream on top. Allow the marshmallow cream to warm and spread out on its own. While waiting, work on the top layer.
For the top layer, make Fruity Pebble bars. Microwave 1 1/2 tablespoons of butter for 20 seconds in a large bowl, until melted. Add 3 cups of mini marshmallows and stir to coat. Microwave for 45 seconds and stir until smooth. (If the marshmallows aren’t completely melted, microwave for an additional 30 seconds.) Mix in 3 cups of Fruity Pebbles. Drop by large spoonfuls over the marshmallow cream layer and carefully spread out evenly. I put my hand in a plastic baggie with a little butter on it and gently spread it out and patted it down.
Notes
Store in an airtight container in the fridge for 4-5 days.