As a newspaper writer and one who loves to study the English language I have been taught to add commas in front of the word 'and' unless it is a conjunction. An example would be: A boy came across some grazing cattle. There was a brindle, a brown, a black and white, and a red.
A comma after each cow's colour but one cow is black and white so the 'and' is a conjunction, therefore no comma is required. The 'and' before 'a red' is not a conjunction.