Place cone-shaped plastic or paper cups inside short drinking glasses for balance. Set aside.
Put the lime gelatin in one bowl and the cherry gelatin in another bowl. Add 1/2 cup of the boiling water to each bowl. Stir with wooden spoons until the gelatin is dissolved. Add half of the can of the frozen fruit juice concentrate to each bowl. Stir until melted. Next stir 1/2 cup of the cold water into each bowl.
Use a measuring spoon to spoon about 1 tablespoon of the cherry gelatin into each plastic or paper cup. Cover each cup with a square of foil. Use a table knife to make a slit in the center of each foil piece. Push a wooden stick through each hole into the gelatin mixture. Put the pops, still in the drinking glasses, in the freezer. Freeze for 1 hour or until firm.
Remove the foil from the cups. Use the measuring spoon to spoon some of the lime gelatin over the frozen cherry gelatin in each cup. Put the pops, still in the drinking glasses, in the freezer. Freeze for 1 hour or until firm.
Repeat alternating layers of cherry and lime gelatin until the cups are full, freezing for 2 to 3 hours after adding the last layer or until firm. Store in freezer up to 5 days.
To serve, hold a cup under warm water for a few seconds, being careful not to get water on the frozen gelatin. Pull the cup off the pop. Makes 8 pops.