Vanilla Filled Cupcakes: this recipe is for gluten free & dairy free, but you could just use the technique for any cupcake you like.
Sparkling Lemon Sandwich Cookies: why not roll them in red, white, and blue sugar? or sprinkles? Or keep the cookies white and change the filling colors?
Red Velvet Cupcakes with Raspberry Buttercream: Raspberries are in or coming into season, and they also happen to be red. Perfect vegan cupcakes for the 4th.
Layer Cake with Mocha Frosting: I made this a rainbow cake last year, but I'm thinking it would be super festive if you made the top three layers blue and white and the bottom three red and white.
Citrus Olive Oil Cake with Chocolate Orange Glaze: perfectly unfussy and very summery tasting
Blackberry Black-Tea Sorbet: cold and refreshing. You could also try Strawberry Sherbet or Lemon Sorbet. The blackberry is definitely the reddest of the bunch, though.
Soy Sauce Marinade: oh you wanted, like, real food? this marinade will jazz up meat, veggies, or tofu. There. You've made yourself a well-rounded meal.