Mix one 3-oz package red jello with 3/4 c. boiling water and stir until dissolved. Add 3/4 c. cold water.
Pour into sprayed 9x13 glass dish. Chill until set.
Dissolve 1 package lemon jello in 1/2 c boiling water. Add 1/2 c cold water. Set aside.
Beat 1 package cream cheese, 2 tbsp half and half, and 3/4-1 c. sour cream until smooth. Slowly add lemon jello mixture, beating in gradually. Carefully, pour 1/2 cream cheese mixture over set red jello. Chill to set. Set other half of cream cheese mixture aside.
Meantime, dissolve lime jello in 3/4 cup boiling water. Add 3/4 cup cold water. Cool to room temp.
When cream cheese layer is set and green jello is cool, pour green jello carefully over cream cheese layer. Chill to set.
When green jello layer is set, gently spread other half of cream cheese mixture over green layer.
Repeat, alternating layers of jello and cream cheese mixture, chilling to set and makiing other 1/2 of cream cheese mixture. End with red jello layer. Top with thawed cool whip. Chill before serving. Cut into squares to serve.