Lightly butter a 9×13 inch baking pan. Set aside.
In a large saucepan, melt the butter on medium heat. Add in the marshmallows, and mix until melted. Mix in enough green food colouring until you reach your desired colour.
Remove from heat, and quickly mix in the rice krispies cereal.
Pour the mixture into the prepared baking pan, and press down evenly. Allow to cool, then cut into squares
Place the chocolate chips in a small bowl. Heat in 30 second intervals in the microwave, mixing after each 30 seconds until the chocolate is completely melted.
Dip each of the rice Krispie squares into the melted chocolate.