Marshmallow fondant is already awesome, but if you add jello to it you can make it even more delicious while coloring it at the same time! Jello seems to mix in really well with the powdered sugar and gives good results for taste and look.
It is really quite simple. You make it the traditional way you make Marshmallow fondant, but you mix in the jello when you melt the marshmallows! Easy and delicious!