The United Kingdom, because it used to be part of the British Empire.
Australia's flag.
UK, Australia, new zealand, Fiji, Samoa, new England
what colour does it represents
The Southern Cross
beacause it is opposite
Australia's flag is predominantly blue, with red and white on the Union Jack, and white stars.
The Union Jack on the flag and the Queen.
The red on the flag is the union jack and it stands for bravery and strength
Jack is another name for a flag, usually a small flag used for signaling, but in the case of the Union Jack it symbolises the union of the three countries - England, Wales, Scotland
The union jack on the Australian Flag is from the first white people to settle on our land, the British. The British flag is JUST the union jack, so, to celebrate the people who first settled in Australia, we have their flag in part of OUR flag. Hope that helps :)
Australia was once a British colony, and so holds the Union Flag within it's flag to represent this. This is the same for all flags which hold the Union Flag as part of their flag. Almost all (with the exception of a small few) countries that were/are part of the Commonwealth were British colonies, and therefore may hold the Union Flag within their own flag.
Wales