As seen here, the three colors of the toppings on a Pizza Margarita represent this Italian symbol
[DOC] [TLE] The Pizza Project: A Taxonomy of the World's Great Pizza Styles ... [PAR] Here are descriptions of the world's most important types of pizza, Neapolitan, ... 
Margherita is the most famous sub-species, with just tomato sauce, cheese, basil, 
... and fresh basil, producing the colors of the Italian flag, red, white, and green.