The flag of the Cocos (or Keeling) islands , a dependency of Australai , was created in 2003 by the local administration and adopted in 2004 officially. This flag is green , has in its centre a crescent , close to the crescent on the right there is the Southern Cross made of yellow stars. On the top on the left, there is a yellow disc which contains a palm tree, with a detail arborescence and a brown trunk.
This flag, clearly have taken the national colours of Australia, strictly: just green ang gold (just in the yellow there is a bit of brown, but it is unsignificant compared with the rest of the flag).
You can have a look to the Cocos flag: http://en.wikipedia.org/wiki/Flag_of_the_Cocos_(Keeling)_Islands I have adapted this flag for making one for entire Australia. The crescent has been replaced by a Commonwealth Star and the palm tree by a blue kangaroo. This is another version adapted from three existent flags which are all a possibility for a national flag: 1970 Papua New Guinea flag, Christmas Island flag and Cocos flag.