Step 1

Bottom (purple) layer:  Dissolve a 3-ounce package of grape flavored jello with 1 teaspoon of unflavored gelatin (1/2 envelope of Knox unflavored gelatin) in 1 cup of boiling water by stirring until completely dissolved.  Pour into a 9x13-inch pan and transfer to the refrigerator.  Make sure the pan is sitting completely flat.  Chill until completely set, about 30 minutes.

Step 2

Second (white) layer:  Make this layer at the same time as the bottom layer. Stir 2 teaspoons (1 envelope) of Knox unflavored gelatin in 1 cup of boiling water until dissolved.  Add 1/2 can of sweetened condensed milk and stir until combined.  Let this sit out on the counter until cooled to room temperature, but not yet set while the previous layer sets up in the fridge.

Step 3

Once the first colored layer has set, make the next colored layer (berry blue) following the directions in Step 1 so it can start to cool.  Then pour 3/4 cup of the white jello mixture over the colored layer and gently tilt the pan side to side for even distribution.  Return jello to the refrigerator to set up, which takes about 20 minutes.

Step 4

Continue to make layers following steps 1 & 2, alternating flavored colorful layers (the next colors in rainbow order are green, yellow, orange, and red) with the creamy white layers, letting the jello set between each addition until all of the jello has been used up.  You will need to make the white layer a couple of times because even without refrigeration it will set up on the counter if you make it all at once.

Step 5

Once the jello is completely set, slice into 1-inch squares using a paring knife (not a serrated blade which leaves marks in the jello) and serve.  A small spatula will help you get the jello cubes out of the pan.