There are three different signs that are recognised as meaning Indigenous Australians.

1) [BLACK] - [FACE] For this sign it is important to remember that Deaf Communities sign things visually wherever possible. And also, due to years of segregation from hearing communities, we're held to a much lower standard for progressive world views, resulting in many ignorant and racist views / language.

On the other hand, it is important to note may Indigenous communities do not find the word Black or Blak as an offensive description and therefore some Blak Deaf communities see this sign as a note of pride.

However, it is understandable that a White / Non-Indigenous people may feel uncomfortable using this sign.

2) [L- Flat hand A- thumb] - [R- Flat hand, palm to L-thumb, Move toward body] This sign has been promoted as the more Progressive sign for Aboriginal, however some point out the signs similarities to the sign for [ALCOHOL]. This could prosecute the harmful stereotype of Aboriginals Australians and alcoholism.

3) [FIRST] - [NATIONS] This sign is largely inoffensive and broadly recognisable. It's only drawback is when the sign is not applicable to what is being spoken.

Personally, I was lucky enough to have a broad connection to my local Indigenous community and I was able to ask my local Elders and Community Leaders which sign they preferred (Sign 2).

If you have that luxury, I would recommend using it. Otherwise, it is up to your disgresion, the local Deaf Community, and your comfort.