Preheat oven to 350°F (175°C).
Line baking sheets with parchment paper.
In a bowl, mix flour, cocoa, soda, and salt.
In another bowl, cream butter and sugars.
Beat until light and fluffy.
Add egg, vanilla, milk, and food coloring.
Mix until smooth and red.
Gradually add dry ingredients to wet.
Mix until dough forms.
Roll dough into small balls.
Coat each ball in sugar.
Place on baking sheet two inches apart.
Bake for 9–11 minutes.
Remove and immediately press Hershey’s Kiss on top.
Cool on rack completely before serving.