I have been using a recipe from Rose Levy Berenbaum's book, "The Cake Bible" for Mousseline Buttercream. For every 5 egg whites, there is 1 cup sugar, 1/2 tsp. + 1/8 tsp. cream of tartar, 1/4 cup water and 1 lb. unsalted butter. Very easy, but slightly involved and very worth the time, effort and energy. I have not had anyone be disappointed with this icing.
However, I think the problem with a meringue icing and colors is not because there is no shortening in them, but the egg whites do not take food coloring very well. Your colors will end up much softer.
Please be aware, this icing DOES NOT CRUST! It is fairly soft, but it will hold up to shell work and roses as long as they aren't too large. Very warm hands will soften it in a decorating bag, so work quickly.
There are variations, including adding chocolate, white chocolate, or fruit purees. All are good. If anyone wants the recipe, ask and I will pull it out for you.
The Client doesn't generally understand the creative process we go through to make them a gorgeous confection ... it really IS more than "just" butter, eggs, and flour!
The Client doesn't generally understand the creative process we go through to make them a gorgeous confection ... it really IS more than "just" butter, eggs, and flour!