Prepare the pan: Lightly grease an 8-inch round cake pan with butter or non-stick spray. Set aside.
Make the orange layer:
In a large pot, melt 1 ½ tablespoons unsalted butter over low heat. Add 3 cups of marshmallows and stir continuously until melted.
Stir in ¼ cup sweetened condensed milk and a few drops of orange food dye, mixing until fully combined.
Remove from heat and quickly stir in 3 cups of rice krispy cereal until coated evenly.
Press the mixture into the outer rim of the greased cake pan, forming a ring. Leave the center empty for the next layers.
Make the yellow layer:
Repeat the same process as the orange layer, using yellow food dye this time.
Once mixed, press the yellow layer inside the orange ring, leaving a small circle in the center for the white layer.
Make the white layer:
For the white center, melt 1 tablespoon unsalted butter with 1 cup marshmallows and 2 tablespoons sweetened condensed milk. Do not add any food dye to keep the layer white.
Stir in 1 cup rice crispy cereal and press it into the remaining space in the middle of the pan.
Chill and slice:
Let the layered rice krispy treats cool and set in the refrigerator for 15-20 minutes.
Once firm, remove from the pan and slice it into 8 pie-shaped triangles to resemble candy corn.