4 kinds of Jello, 2 pkgs. each kind

Mix 1 package of each color Jello with 3/4 cup hot water and 3/4 cup cold water. Mix 1 package of each color with 3/4 cup hot water and 3/4 cup evaporated milk. Put in layers in 9"x13" pan, 1 with water, 1 with milk. Let set between each layer. Cut in serving pieces and top with Cool Whip.