Preheat oven to 350 degrees F. and line a muffin tin with cupcake liners.
In a large bowl, mix the eggs, buttermilk, blue food coloring, sugar, and oil.
In a separate bowl, mix the flour, salt, and cocoa powder.
Add the flour mixture to the buttermilk mixture and mix until well combined. Don't overmix.
In a small bowl, combine the baking soda and vinegar. Once it foams up, fold it into the cake batter.
Coat the blueberries with a tbsp of all-purpose flour, discard any excess flour. Fold the blueberries into the batter.
Divide the batter evenly into your prepared muffin tin and bake for 18-20 minutes or until a toothpick inserted in the center comes out clean or with fine crumbs.
Allow the cupcakes to cool completely before frosting and enjoy!