We completed our paper on Smarties Sandwiches in August 2022 and submitted it for publication. Once it is published, we will post the link to it here! In the meantime, here is the abstract.
Smarties come in packages of fifteen candies in up to six different colors. One fun Smarties tradition is to open the pack and form "sandwiches" out of them before eating the candies. Each sandwich consists of three candies --- the two "buns" must be the same color and the "filling" must be a different color from the buns. What is the probability of getting an unsandwichable roll? In this article we answer this question and prove some theorems relating to the sandwichability of Smarties rolls.