Line cookie sheet with waxed paper. In 2-quart saucepan, melt peanut butter chips over low heat, stirring constantly, until smooth. Remove from heat. Stir in frosting and icing color until well blended. Refrigerate until cool enough to handle, about 1 hour.
Shape mixture into 1 1/4-inch balls; flatten slightly. Use edge of rubber spatula to make grooves in each ball to resemble pumpkin. Press 1 pretzel piece into top of each for stem; place on cookie sheet. Refrigerate at least 1 hour before serving. Store in covered container in refrigerator.