Grease an 8x8-inch glass baking dish. Divide 2 cups of Rice Krispies cereal into 3 separate bowls, set aside.
Place 1/3 of the marshmallows and 1/3 of the butter into a large microwavable bowl. Melt in the microwave on high for a about a minute, or until they begin to get big and puffy and the butter is melted, watch carefully. Remove the bowl from the microwave.
Using a tooth pick, add the green food coloring, stir until combined and the desired color is reached. Immediately stir in 2 cups of Rice Krispies, mix well.
With buttered hands, press the mixture into the prepared baking dish.
Repeat steps 2-4 for the second layer, but do not add food coloring to this layer. This is the white layer.
Repeat steps 2-4 for the blue layer, adding a bit of violet to achieve the desired color of blue.
Wash and dry your hands. Press the Skittles candies into the Rice Krispies Treats. Allow to cool, cut, serve, and enjoy!