Melt 3 tbsp butter and marshmallows in a pan over medium-low heat, stirring constantly, until almost smooth. Add green food coloring slowly to desired color. Once completely smooth remove from heat and stir in Rice Krispies until completely coated. Using the softened butter, rub on your fingers then press the mixture into a greased 9" x 13" dish. Immediately top with sprinkles. Let cool for 30 minutes. Cut into triangles with a greased knife or greased cookie cutter. Insert popsicle stick or stem of your choice and serve.