From Ausflag‘s page on the (Australian) Aboriginal Flag:
The Aboriginal Flag was designed by Harold Thomas, an artist and an Aboriginal, in 1971. The flag was designed to be an eye-catching rallying symbol for the Aboriginal people and a symbol of their race and identity. The black represents the Aboriginal people, the red the earth and their spiritual relationship to the land, and the yellow the sun, the giver of life.
In the late 1960s, Aborigines stepped up their campaign for indigenous land rights through protest marches, demonstrations, banners and posters. The protests increased in the early 1970s and Harold Thomas noticed they were often outnumbered by non-Aborigines with their own banners and placards. He decided they needed to be more visible and the idea of the flag was born.
The Aboriginal flag was first raised in Victoria Square in Adelaide on National Aboriginal Day in 1971, but was adopted nationally by Aborigines and Torres Strait Islanders in 1972 after it was flown above the Aboriginal “Tent Embassy” outside of the old Parliament House in Canberra.
Mr Thomas has often been asked to design a new Australian flag, but he says the design of the Aboriginal flag “sprung from passionate times” and that his inspiration could not necessarily “be repeated” for a new Australian flag. Mr Thomas says he would prefer to see something different for a new Australian flag.
Mr Thomas is also uneasy about suggestions that the Aboriginal Flag could replace the Union Jack in the current Australian flag to create a new national flag. Mr Thomas says “Our flag is not a secondary thing. It stands on its own, not to be placed as an adjunct to any other thing. It shouldn′t be treated that way.”
The Aboriginal flag is increasingly being flown by both Aboriginal and non-Aboriginal people. In view of its increasing importance in Australian society, the Government initiated steps in 1994 to give the flag legal recognition. After a period of public consultation, the Government made its own decision in July 1995 that the flag should be proclaimed a “Flag of Australia” under section 5 of the Flags Act 1953. The flag was so proclaimed by the Governor General of Australia, William Hayden, on 14 July 1995.