1. Preheat oven to 325 degrees Fahrenheit. Line two baking sheets with parchment paper.
2. Using a hand-held mixer, cream butter, sugar, and cream cheese. Beat in egg yolk and vanilla.
3. Slowly incorporate flour.
4. Divide batter into batches for however many different colors you want to dye your cookies.
5. Add drops of food coloring to batches until you have achieved desired hue.
6. Mold batter into one-inch balls. Coat with decorations if you're feeling fancy.
7. Space evenly on baking sheet. Bake approximately 11-13 minutes.