Actually the link SamBam has provided, i.e. to https://en.wikipedia.org/wiki/National_colours_of_Italy , explains the tricolour better. It also says "An apocryphal story about the history of pizza holds that on 11 June 1889, Neapolitan pizzamaker Raffaele Esposito created a pizza to honour Margherita of Savoy, who was visiting the city. It was garnished with tomatoes, mozzarella, and basil to represent the national colours of Italy, and was named 'Pizza Margherita'".