Know the colors of the rainbow.  Red, Orange, Yellow, Green, Blue & Purple.  Using the quick set method {ice cubes} prepare the purple jello first. Pour about 1/4 cup of prepared Jello into each glass.  FYI: I used the large boxes of Jello and this recipe made 8 glasses of rainbow jello, plus {1} 8×8 Pyrex dish.

Place the glasses in a baking pan, and refrigerate for 30 minutes.

Add food coloring to 6 separate bowls of cool-whip or yogurt {one for each color of the rainbow}.

Remove the cups of the Jello from the refrigerator and add a thin layer of colored whipped topping or yogurt on top of the Jello.  You want to match the color of whipped topping/yogurt to the colored Jello below.

Working in reverse order, add the next color of Jello .  Refrigerate.  Repeat steps 4 & 5 until you have refrigerated the last layer {red} of Jello.  Once the red Jello has set, then add a dollop of whip cream to the top.  And a spoon and dig in.