I know there are other questions comparing the US and UK usage of o and ou in words like colour. My question is specifically in regard to Australian English. I was always taught that here in Australia we use ou and that the other variant was yet another example of the insidious corruption of civilization as we know it by our cousins across the water. However, recently I've been reading old newspaper reports from the early 1900s and have consistently found them writing color, honor, etc. I wonder if anyone knew when and why this changed.
Well, you missed off the connected question, why is the spelling of the Australian Labor Party using the 'or' form. Wikipedia is inconclusive on the topic. From what I read on it while researching the ALP it was either a homage to the US labor movement or it was a common spelling at the time.
I think it is probably due to editorial decisions at newspapers from that time because the same usage does frequently occur in Australian books from the same period. If anyone has a copy of any Australian style guides or editorial guidelines from that time I'm sure we could answer this question.
I have some dictionaries and books on writing from late 19th century so I'll update this later if I find anything.
Don't dismiss the inability of editors in small town and regional newspapers as a possibility either. Australia has a long history of incompetence in that department.
Update 1: I found this article which references an article from before Australian Federation (pre-1901) that blames the problem on the availability of American dictionaries. The article cites papers that I can't find online but they are probably hiding in some upstairs section of a university library.
The change from American spelling to British spelling is, surprisingly, a recent phenomenon in Australia. It was standard for most of the 20th century for Australian newspapers to prefer the '-or' ending to the '-our' ending. Strangely, words such as 'centre' and 'theatre' were generally spelled in the British style. It is only in recent years that Australian newspapers have begun using the British '-our' endings. Perhaps contacting the newspapers directly would help shed some light on the subject. Also, it wasn't just newspapers that preferred the American '-or' endings. Magazines such as TV Week advertised their 'full color' poster each week, while Channel 9 proudly displayed the logo 'Living Color' from 1975 onwards for several years after the introduction of color television in Australia. In fact, you'll find an example of this 'Living Color' logo on the internet (a blast from the past!). I have a dictionary published by the Herald and Weekly Times setting out its standard for Australian spelling. It reflects the spelling usages above. Many younger Australians may be surprised to learn that the change of usage from American to British spelling and grammar in Australia is a very recent phenomenon.