Preheat oven to 350ºF. Line four 6-inch round baking pans with parchment paper, and spray with nonstick cooking spray.

In a mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt until combined; set aside.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium speed until pale and fluffy. Beat in the eggs, one at a time, until combined, scraping down the sides and bottom of the bowl as needed. Beat in the sour cream, vanilla, and vinegar on medium speed.

Pour the dry ingredients into the wet ingredients and mix until combined. Whisk the food colorings into the buttermilk, then pour it into the batter. Mix until just combined, scraping down the sides and bottom of the bowl as needed.

Divide batter among the four cake pans. Bake for 25-27 minutes or until a toothpick inserted in the center comes out clean. Allow to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, cream cheese, vanilla, and almond extract together on medium-high speed until smooth, 2-4 minutes. Gradually add in the powdered sugar, one cup at a time, and continue beating until creamy.

Using a serrated knife or a cake leveler, trim off the the tops of the cakes to create a flat surface. Crumble these scraps into small crumbs; set aside.

Place one cake layer onto a cake plate or pedestal. Spread a layer of cream cheese frosting on top. Press fresh blueberries randomly throughout the frosting layer. Repeat steps with the remaining cakes, frosting, and blueberries.

Frost the sides and top of the cake. Press the cake crumbs all over the sides of the cake until covered. Pipe frosting rosettes around the top border, if desired. Keep cake covered and refrigerated until ready to serve.