Open each Rice Krispie Treat and discard the packaging.
Line a large baking sheet with parchment paper.
Open and pour the Wilton green candy melts into a microwave-safe dish. Heat in the microwave in 30-second increments, stirring until melted.
Dip each Rice Krispie Treat into the green melted chocolate to coat. Lift the treat using a fork and allow the excess chocolate to drip back into the bowl. Place on the parchment-lined baking sheet. Repeat with the other Rice Krispie Treats.
Place the Rice Krispie Treat in the fridge for 20-25 minutes to set.
Pour the black candy melts into a microwave-safe dish and repeat melting instructions.
Allow the melted chocolate to cool a few minutes and scoop into the sandwich bag. Snip the corner and gently squeeze the chocolate out making 2 triangles for eyes, a small triangle for a nose and a mouth for each Jack-o-Lantern treat.