The People's Flag: The Red or Civil Ensign
The flag below is recognised worldwide (apart from some confusion with the New Zealand flag) as the official Australian National Flag, also referred to as the Blue Ensign. The Blue Ensign has been the official Australian national flag since 3rd September 1901, with a couple of changes since that first flag. However, until 1954, the Blue Ensign was for use only by government officials.

At the same time as the Blue Ensign was adopted as the national flag, the Red Ensign was adopted as the official merchant naval flag, and is identical to the Blue Ensign bar the background colour:

Unfortunately, lost to recent history is the fact that up until 1954, Australian citizens could not fly or use the Blue Ensign in any capacity. The Blue Ensign was only for official government use, much like the Coat of Arms still is to this day.
Many citizens continued to fly the British Union Jack, but when a more ‘Australian’ flag was required, people turned to the Red Ensign. While always the official flag for the merchant navy, it became the unofficial flag of the people — even soldiers fought under the Red Ensign in both world wars.
The 1917 photo of ANZACs below shows this well. The field (or background) of the flag is the same shade of grey in the black & white photo as the red parts of the Union Jack. Additionally, the field is a noticeably different shade of grey to the blue parts of the Union Jack. These two factors in a b&w photo tell us that the photo is of a Red Ensign rather than the blue flag that we today are used to.

Attribution: National Library NZ on The Commons, No restrictions, via Wikimedia Commons
Where once the colour red was associated with the British Empire on maps, it soon became synonymous with the rise of communism after World War II. To counter this, and apparently without consulting Australian citizens, the then Prime Minister of Australia, Robert Menzies, made the Blue Ensign the national flag for all in 1954.
Despite this, the Red Ensign is not completely forgotten as the people’s flag. It is proudly flown by Australians to this day, as the flag their ancestors knew as Australians. The Liberty Party honours its memory and history by including it in the party logo.
Please go here (external site) for more history and imagery about this iconic Australian flag.