Place marshmallows and butter in a large microwave safe bowl. Microwave at 30 second intervals until fully melted. Carefully stir in cereal (you may need to divide this into two batches if you don't have a bowl big enough).
Divide mixture into thirds. Leave one third plain, then use red and green gel food coloring to tint the mixture.
Cut three sheets of paper, approximately the size of a cookie sheet. Working with one color at a time, press the mixture flat to a thickness of 1/2-3/4", using another sheet of parchment over top to help.
Use cookie cutters to cut out desired shapes, leaving the cutters in the Rice Krispie mixture. Peel the excess away from the cutters and gently push the shapes out of the cutters. Set aside. You can smush your scraps back together to make more shapes, you may need to re-warm in the microwave for 30 seconds.
In small microwave safe bowls, pour in the candy melts (I used red, green, white and black). Melt in microwave for one minute, stir, then at 30 second intervals until completely melted and no lumps remain. Spoon mixture into small Ziploc bags, Cut the tip of one corner off, but just enough to make a small hole.
Decorate cutouts , embellishing with sprinkles as desired.
To make ornaments: use a straw to punch out a hole in the cutout. Cut approximately 8 inches of thin ribbon and knot the ends together. Thread the looped ribbon through the hole and push the knotted end through the loop. Gently pull to tighten. Decorate as desired. Leave out overnight before hanging.