I do a lot of editing at work, and one of the main annoyances I see over and over again is the missing comma before a conjunction in a series of three or more items: red, white and blue. Unless you are writing a newspaper article, a proven venue for saving space, in most American style guides, this is incorrect grammar usage and is considered the Wrong Rule. The phrase should read: red, white, and blue.
Now before you get riled and swear to me that everyone has accepted this grammatical faux pas, that it’s a matter of preference, let me cite the sources I use as my foundation.
» Chicago Manual of Style
» American Psychological Association (APA) Style
» The MLA Handbook for Writers of Research Papers
» Elements of Style
» Modern American Usage: A Guide.
» A Manual for Writers
» Gregg Reference Manual
» Scientific Style and Format
Most people who argue for ommision quote from newspaper style guides, which include the Associated Press (AP) Stylebook. Some British writers also have jumped on this grammatical band wagon. You might ask why most American standard usage keeps this vital comma. The reason is to prevent confusing combinations of the final two words: eggs, bacon, and toast. “Bacon and toast” is not one idea. If I write eggs, toast and jam, and bacon or eggs, bacon, and toast and jam, the potential confusion becomes apparent.