To me, the most versatile dessert sauce is Creme Anglaise. Lay it down as a base, dessert on top, then decorate with your colored fruit sauces–these need be nothing more than a sweetened or spiked fruit puree.
2/3 cup sugar
1/2 teaspoon cornstarch
4 egg yolks, lightly beaten a pinch of salt
2 cups scalded milk
1 teaspoon vanilla extract
Mix the sugar with the cornstarch
Combine the sugar mixture, egg yolks and salt in the top of a double boiler
Stir in the the scalded milk
Cook over simmering water until the mixture coats a metal spoon
Allow the sauce to cool slightly
Stir in the vanilla
Store in the refrigerator with plastic wrap pressed onto the surface of the sauce
I have found that this freezes pretty well, too, believe it or not.