Mix each package of jello, separately, with 1 cup boiling water. Divide in half. Pour first half in pan. Chill in freezer for 10 to 15 minutes. Mix second half with 1/3 cup sour cream or Cool Whip. Pour over first layer; chill. Continue layers alternately until all 12 layers are done.
Can use red and green for Christmas or orange and purple for Halloween.