To make red layer, pour 1 cup water into 1-quart saucepan. Sprinkle unflavored gelatin over water. Let stand 1 to 2 minutes to soften. Heat over low heat about 5 minutes, stirring constantly, until gelatin is dissolved. Remove from heat. Stir in flavored gelatin until dissolved. Stir in vodka. Pour into 13x9-inch cake pan or 48 flexible silicone mold cups. Refrigerate until fully set, about 1 hour.