Place plantains in a pot with water to cover. Bring to a boil; cook until tender, about 15 minutes. Drain, transfer to a bowl, and mash until smooth. Add 1/2 cup white sugar, vanilla extract, cinnamon, and red food coloring.
Preheat the oven to 400 degrees F (200 degrees C). Flour a pie plate; line the plate with the pie crust.
Pour the plantain mixture into the pie crust. Arrange sliced mangos on top and sprinkle with a pinch of sugar.
Bake in the preheated oven until mostly firm, about 30 minutes.