My daughter used to do that. When it was almost set, she whipped theJell-O with beaters until it was very foamy. Then she poured it into the container or containers. (Parfait glasses?) When that sets, there is some clear Jell-O on the bottom and foam on the top. Then she poured on more clear cooled Jell-O, perhaps in a different color. That made three different colors, as the foamy stuff is a much lighter color from the bottom stuff.