Heat oven to 375 Degrees F.
In a large bowl cream butter, peanut butter, and white sugar. Stir in egg, milk, vanilla, and food coloring.
Stir in baking soda, salt, and cocoa. Gradually mix in flour a little at a time. Mix until just combined.
Roll dough into one inch balls. Then roll dough in red sanding sugar, and place on un-greased cookie sheet.
Bake for 8 to 10 minutes or until the edges are set.
When cookies are done baking, immediately press a Hershey's Kiss in the center and push down until the cookie cracks.