Melt 1 ½ tablespoons of butter with 1 ¼ cups of marshmallow in a microwave for 45 seconds.
When butter is melted, stir together butter and marshmallows until completely combined. Add 3 drops of desired gel coloring.
Add 1 ½ cups of Rice Krispie cereal to marshmallow cream. Stir until rice cereal is evenly coated.
Spray plastic Easter eggs with oil and pack tightly with coated rice cereal mixture. Close the plastic egg and let sit for 10 minutes. Remove plastic egg shell and set aside.