Barn: Trim 1 side of square cake to form roof of barn; place cake near top of tray with roof at top of tray. Spread thin layer of red frosting over entire cake to seal in crumbs. Refrigerate or freeze cake 30 to 60 minutes. Frost sides and top of cake with remaining red frosting. Make vertical lines on top of cake to look like boards (use spatula or toothpick).
For window, break 2 pretzel sticks in half; place near top of cake in square shape.
For shutters, place 1-inch-square piece of graham cracker on each side of window.
For sides and top of doorway, place 3 pretzel sticks near bottom of cake.
For doors, place 2 1/2x1-inch graham cracker rectangle on each side of doorway.
For roof, arrange eight 2 1/2 x1-inch graham cracker rectangles on top edge of cake, overlapping to form barn roof shape.
For hay, place 1/2 cup of the coconut in resealable food-storage plastic bag. Add 2 drops yellow liquid food color; seal bag and shake to mix. Place small amount of yellow coconut at bottom of window and doorway (reserve remaining yellow coconut to decorate chick cupcakes).
For grass, place remaining 1 cup coconut in resealable food-storage plastic bag. Add 2 drops green liquid food color; seal bag and shake to mix. Scatter green coconut on bottom half of tray. Decorate cupcakes and arrange on coconut grass.