Prepare 8x8-inch baking dish with parchment paper leaving 2-inch overhang on all sides.

In large pot, melt butter over medium-low heat. Once butter stops foaming, add package of marshmallows (leaving remaining ½ cup for later) and continue to cook, stirring constantly, until fully melted.

Remove pot from heat and stir in food coloring, vanilla and salt until mostly uniform.

Add cereal, remaining ½ cup marshmallows and sprinkles, reserving some for top, and fold until well combined. (Note: Don’t worry if there are still globs of melted marshmallow.)

Transfer mixture to prepared baking dish and press into even layer. If desired, add more sprinkles to top and gently press to adhere. Cool to room temperature, about 1 hour.

Remove treats from pan by lifting parchment paper. Slice into squares or use cookie cutters to make shapes.