01 - Preheat oven to 350°F (175°C).
02 - Blend graham cracker crumbs, granulated sugar, and melted butter in a mixing bowl. Press firmly and evenly onto the bottom and sides of a 9-inch pie dish.
03 - Bake the crust for 8 to 10 minutes until light golden brown. Remove from oven and allow to cool entirely.
04 - In a large mixing bowl, beat softened cream cheese until smooth. Incorporate powdered sugar, sour cream, and vanilla extract, mixing until uniform.
05 - In a separate bowl, whip cold heavy cream to stiff peaks using an electric mixer or hand whisk.
06 - Gently fold the whipped cream into the cream cheese mixture until smooth. Separate filling into three equal portions.
07 - Leave one part white, tint the second portion with red gel food coloring, and the third with blue gel food coloring, stirring each until color is even.
08 - Drop spoonfuls of each colored filling alternately over the cooled crust. Using a skewer or knife, gently swirl the colors to create a marbled appearance, avoiding overmixing.
09 - Smooth the surface with a spatula and refrigerate for at least 2 hours until firmly set.
10 - Before serving, top with whipped cream and arrange halved strawberries and blueberries as desired.