Line a 9”x13” baking dish with parchment paper and butter the paper. You only need about a tablespoon of butter and you can just spread it over the paper.
Melt 4 tablespoons of butter into a saucepan on low heat. Add the marshmallows to the butter and stir until they are melted into the butter.
Remove from heat and stir in 4 to 6 drops of green food coloring and vanilla.
Immediately add the rice krispie cereal into the marshmallow mixture and stir until all of the cereal is well coated.
Spread the rice krispie treat mixture onto the pan and press the treats down to compact them.
Add your sprinkles to the top of the treats. Allow them to cool for about 10 to 15 minutes. Cut into squares or fun shapes and serve!