Lightly grease a 9×13 inch pan and set aside.
Rice Krispie Layer: In a large saucepan, melt the butter on medium heat.
When the butter is melted, add in the marshmallows mixing constantly until melted.
Remove from heat and add the red food coloring to your desired color. Fold in the Rice Krispie cereal until full combined.
Drop the mixture into the prepared pan, and press down evenly. Allow to cool.
Buttercream Filling: In a medium bowl, beat the butter until light and fluffy. Add in the icing sugar, and beat until smooth.
When the Rice Krispie layer is cool, cut in half. Spread the frosting on one side, and place the other side on top.
Cut into squares, and store in an airtight container for up to 2 weeks.