In 2-quart saucepan, place potatoes; add enough water just to cover potatoes. Heat to boiling; reduce heat. Cover and simmer 18 to 20 minutes or until tender; drain. Mash potatoes with potato masher or electric mixer on medium speed. Add butter and milk. Stir until light and fluffy. Add salt. Stir in food color.
Place mashed potatoes in gallon-size resealable food-storage plastic bag. Cut about 1-inch hole in 1 corner of bag. Pipe “snakes” onto serving plates. Place 2 olive slices on one end of snake for eyes. Cut pimiento in half for snake tongue. Serve immediately.