About a dozen of us were staying overnight at the Tias' in Sundsvall. Since it was a week or two before Christmas (1988), they kindly served us some traditional risgrynsgröt in the kitchen. Elder Jackson asked Sister Tia for some milk to put on his gröt, and she handed him a carton from the fridge. When he poured green milk onto his gröt, we were all surprised, but Elder Jackson howled with laughter. When he could breathe again, he explained that Sister Tia had deliberately reminded him of an experience he had had when a greenie.
Elder Jackson's first companion took advantage of the inexperience and naïvete of a new missionary by devising a diabolical practical joke. In that part of Sweden, as in most other parts, milk cartons were color coded according to fat content. Whole milk was red, skim milk was blue, and mellanmjölk ("middle milk") was green. Elder Jackson's companion injected cartons of mellanmjölk with green food coloring and told his young companion that the green cartons had green milk in them. He perpetuated this deception by enlisting the help of members and even investigators, so that wherever the two ate dinner, there would always be green milk.
Eventually Elder Jackson refused to buy the green milk anymore, and presumably he discovered the truth sometime before that diverting experience in the Tias' kitchen.
Story: Lee Choquette