01 - Preheat oven to 350°F.
02 - In a mixing bowl, combine graham cracker crumbs, granulated sugar, and melted butter. Mix until evenly moistened, then press firmly onto the bottom and up the sides of a 9-inch pie dish.
03 - Bake the crust for 8 to 10 minutes until lightly golden. Remove from oven and allow to cool completely on a rack.
04 - In a separate large bowl, beat softened cream cheese until smooth. Add powdered sugar, sour cream, and vanilla extract, and beat until thoroughly combined and creamy.
05 - With clean beaters, whip the cold heavy cream in another bowl until stiff peaks form.
06 - Gently fold the whipped cream into the cream cheese mixture until smooth. Divide the filling evenly among three bowls. Leave one plain, tint one with red gel food coloring, and tint the last with blue gel food coloring, mixing until colors are uniform.
07 - Drop spoonfuls of each colored filling alternately onto the cooled crust. Using a skewer or knife, gently swirl the colors together to create a marbled effect without overmixing.
08 - Smooth the top of the filling and refrigerate for at least 2 hours until set.
09 - Before serving, pipe or dollop whipped cream onto the surface. Garnish with halved fresh strawberries and blueberries as desired.