Preheat oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a large bowl, mix together flour, sugar, baking soda, salt, and cocoa powder.
In a separate bowl, whisk together oil, buttermilk, egg, food coloring, vinegar, and vanilla.
Gradually add the wet ingredients to the dry ingredients, stirring until just combined.
Fill cupcake liners 2/3 full and bake for 18-20 minutes, or until a toothpick comes out clean.
Let the cupcakes cool before frosting with cream cheese frosting. Decorate with heart-shaped candies if desired.