Preheat oven to 350°. Spray a 13x9-inch baking pan with nonstick baking spray with flour.
In a large bowl, combine butter and sugar. Beat at medium speed with an electric mixer until fluffy. Add eggs, one at a time, beating well after each addition.
In a medium bowl, combine flour, cocoa, baking soda, and salt.
In a separate bowl, combine buttermilk, vinegar, and vanilla. Add flour mixture to butter mixture, alternately with buttermilk mixture, beginning and ending with flour mixture. Add red food coloring, beating until well combined.
Spoon batter into prepared pan. Bake for 25 to 30 minutes or until a wooden pick inserted in center comes out clean. Let cool in pan on a wire rack for 10 minutes. Remove from pan, and let cool completely on wire rack.
Crumble cake, and layer with Coconut Mousse in parfait glasses. Garnish with toasted coconut, if desired.
Recipe by Southern Lady Magazine at https://southernladymagazine.com/red-velvet-parfaits-recipe/