Mix 1 teaspoon unflavored gelatin powder with one package (3 oz) of jello powder.
Pour 1 cup boiling water into the powder and stir until powder is dissolved.
Pour jello mixture into a baking dish or individual cups. Put the jello in the refrigerator to set.
Step 2: White layer
Mix unflavored 2 teaspoon gelatin powder with 1 cup boiling water and stir til dissolved.
Stir ½ a can sweetened condensed milk into the gelatin mixture. Let it cool to room temperature.
When the first jello layer is fully set (30 minutes) pour the room temperature white layer evenly over the first jello layer.
Next, return the dish to the fridge to set and begin preparing the next jello layer. (Refer to step 1)
Repeat steps 1 and 2 until you have poured all of your rainbow layers.
Video
Notes
this recipe uses 3 oz. boxes of Jello and 14 oz. cans of sweetened condensed milk
Stir together the flavored jello and gelatin before adding the hot water. This is to avoid the gelatin clumping together.
If you're making jello in individual cups, put the cups onto a baking sheet or arrange them in a baking dish to make it easier to transfer them back and forth from the fridge to the countertop.
For beautiful layers:
Make sure that you refrigerate each layer sufficiently before adding the next layer.
Cool jello mixture to room temperature before pouring it on top of a chilled layer.
Pouring hot (or even warm) jello mixture onto a previous jello layer will result in the jello mixing together and ruining the clean, layered jello look.