HEAT oven to 350°F.
PREPARE cake batter as directed on package; tint with food coloring. Pour evenly into 2 greased and floured 9-inch round pans.
BAKE as directed on package. Cool in pans 10 min.; remove to wire racks. Cool completely.
BEAT cream cheese and powdered sugar with mixer until well blended. Stir in COOL WHIP with whisk. Spread onto tops and sides of cakes.
CUT each cake into 8 wedges to resemble Christmas trees. Insert peppermint stick into curved side of each cake for the tree trunk. Decorate with remaining ingredients.