Prepare the Jello and custard per package directions.
In tall dessert cups, place a 1/2" layer of the sponge cake.  Soak the layer of cake in Jello.  Spoon on a thin layer of raspberry jam.  Add a layer of custard.
Continue adding layers of sponge cake, jam, and custard until the cup is full (with a layer of custard on top) -- 2 to 3 layers.
Chill for 2 hours.  Sprinkle colored sugar on top and serve.