In a large saucepan, melt the butter over low heat. Add the mini marshmallows and stir until completely melted and smooth. Remove from heat.
Quickly add the crispy rice cereal to the melted marshmallow mixture and stir until well combined.
Gently fold in the freeze-dried strawberries and blue raspberry candy until evenly distributed.
Press the mixture into a greased 9x13-inch baking dish, using a spatula or your hands (dampened with water) to flatten it evenly.
If using, melt the white chocolate chips in a microwave-safe bowl in 30-second intervals, stirring in between until smooth. Drizzle over the top of the treats.
Allow the treats to cool completely at room temperature, then cut into squares or rectangles.