Drain plums, reserving 1 cup syrup. Peel plums and remove pits. Place in a food processor, cover and process plums until smooth.
In a large bowl, combine the milk, cream, sugar, lemon juice, plums, reserved syrup and food coloring if desired. Stir until sugar is dissolved.
Fill cylinder of ice cream freezer two-thirds full; freeze according to manufacturer's directions. Refrigerate remaining mixture until ready to freeze. Allow to ripen in ice cream freezer or firm up in refrigerator freezer for 2-4 hours before serving.