Which one is correct and natural?

1) Please itemize all jacket purchases by price, color, and size.
2) Please itemize all jacket purchases by price, color and size. (Without a comma in front of and)

See a translation

This is a matter of personal preference (and your editor/manager/teacher's preference). The comma before "and" is called the "Oxford comma", and writers are split about whether or not it's necessary.

In this case, it's not strictly necessary, since it's easy to tell that it's a list of three items. However, in a case like this:

Once you're finished, send the itemized list to the managers, Dave, and Jessica.
Once you're finished, send the itemized list to the managers, Dave and Jessica.

the lack of a comma in the second version might imply that the managers are Dave and Jessica, rather than two additional people who need the list. In this case, the comma is mandatory.