Absolutely right, the yellow coloring makes the finished pizza look more appealing, and the yellow color infers richness, both desirable characteristics. Large wholesale manufacturers have stipulations governing the use of yellow coloring. For the most part, if the product contains eggs they cannot use the coloring, but if it does not contain eggs, they can use it. The reasoning? One egg in 2,000-pounds of dough and 1-gallon of egg shade coloring and it looks like the dough is made with buku whole egg. But if the formula doesn't contain any eggs, then eggs are not on the label, and they are free to use it. Truth of the matter is that it is all but impossible to get the color of egg shade in a dough through the use of whole eggs, whole eggs just don't contribute that much color to the dough.
Tom Lehmann/The Dough Doctor