Spray a 9- x 13-inch pan with cooking spray.
Melt 5 tablespoons butter over low heat in a large saucepan (3-quart capacity or larger). Add the marshmallows and cook, stirring constantly, until almost melted. Remove the pan from the heat and immediately stir in the Lucky Charms™ cereal.
Pour the mixture into the prepared pan. Press the mixture down with a rubber spatula until it fits evenly in the pan. Cool about 30 minutes.
Microwave the almond-flavored candy coating as directed on the bag. Stir in 2 to 3 drops of green food color.
Cut the cooled cereal bars into 16 equal pieces. Dip the bottom of each bar into melted candy coating. Place the dipped cereal bars, coating side up, on a sheet of waxed paper. Let them stand until the coating is set.