Preheat the Oven: Preheat your oven to 325°F (163°C). Grease a 9-inch springform pan and line the bottom with parchment paper.
Prepare the Crust: In a medium bowl, mix the graham cracker crumbs, sugar, and melted butter until well combined. Press the mixture firmly into the bottom of the prepared pan to form an even layer. Bake the crust for 10 minutes, then set aside to cool.
Make the Cheesecake Filling: In a large bowl, beat the cream cheese and sugar together until smooth and creamy. Add the vanilla extract and eggs, one at a time, beating well after each addition. Finally, mix in the sour cream until just combined.
Divide and Color the Filling: Divide the cheesecake filling into three equal parts. Leave one part plain, and color the other two parts with red and blue food coloring, respectively.
Fill the Pan: Pour each color into the crust one layer at a time ----------------------------------OR------------------------------------------------------------------Create the Swirl Effect: Drop spoonfuls of the plain, red, and blue cheesecake filling into the crust. Use a knife or a skewer to gently swirl the colors together to create a marbled effect. Bake: Place the springform pan in a larger roasting pan. Pour hot water into the roasting pan to come about halfway up the sides of the springform pan (this is called a water bath and helps prevent cracking). Bake in the preheated oven for 55-65 minutes, or until the center is set and the edges are lightly browned. Turn off the oven and leave the cheesecake inside with the door slightly ajar for 1 hour to cool gradually. Then remove the cheesecake from the water bath and refrigerate for at least 4 hours or overnight to fully set.
Decorate and Serve: Before serving, top with fresh strawberries, blueberries, and whipped cream. Carefully remove the cheesecake from the springform pan and transfer to a serving platter. Slice and enjoy!