Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a medium bowl, sift together the flour, sugar, baking soda, salt, and cocoa powder. Set aside.
In a large bowl, use a handheld mixer to beat together vegetable oil, buttermilk, eggs, red food coloring, vinegar, and vanilla extract. Add purple food coloring until desired color is reached.
Gradually add the sifted dry ingredients to the wet mixture, mixing until smooth and combined.
Divide the batter evenly between the prepared pans. Bake for 25-30 minutes, or until a toothpick comes out clean. Let cakes cool on a wire rack for 10 minutes, then remove from pans to cool completely.
For the frosting, beat softened cream cheese, butter, and vanilla in a large bowl until smooth. Gradually add confectioners’ sugar, beating until light and fluffy.
Once cakes are fully cooled, frost generously with cream cheese frosting, covering top and sides.