Virtual
War Memorial
Australia

Members of the Australian Imperial Force who served on Gallipoli will be entitled to wear over the Unit “Colour Patch” on both sleeves of the Service Dress Jacket and Greatcoat the letter “A” an indication that the wearer had taken part in the operations on the Gallipoli Peninsula.  - Military Order 354 of 1917

Members of the Australian Imperial Force who served on Gallipoli or the Islands of Lemnos, Imbros and Tenedos, or who have served on transports or hospital ships at or off Gallipoli or the Islands above-named, or in AIF lines of communication Units in Egypt will be entitled to wear over their Unit “Colour Patches” on both sleeves of their Service Dress Jacket and Greatcoat the letter “A” as an indication that the wearer had taken part in the Gallipoli operations. - Military Order 20 of 1918

Robert Kearney

The colour patches which identified units in the AIF were designed to show what division or service they belonged to, and also, in the case of infantry units, their brigade and the sequence of the Battalion in that Brigade.

The shape of a colour patch indicated the division or service -
1st Division - horizontal rectangle split horizontally
2nd Division - diamond shape split horizontally
3rd Division - horizontal ellipse
4th Division - circle split horizontally
5th Division - vertical rectangle split vertically.

The lower colour denoted the brigade's sequence in the Division. Usually (but not always!) these colours were:
Green - first brigade in the division
Red - second
Light Blue - third

The 4th Brigade, originally in the 1st Division , had a dark Blue lower half. Its reallocation to the 4th Division after Gallipoli threw both the brigade / battalion numbering sequence (the most logical at any time in the history of the ADF) and the colour patch structure into disarray!

In the first AIF there were four infantry battalions to each brigade, and the upper section (or LHS in the case of the 5th Division) of the colour patch identified each one. Usually (but not always!) these colours were:
Black - first
Purple - second
Brown - third
White - fourth

Thus every battalion had a unique colour patch.

Other Arms and Service Corps had variations but those attached to the five divisions generally incorporated the shape of their parent Ddvision.

Source: Text taken from The 27th Battalion Centenary: The Historical Record of the 27th Battalions 13th August 1877-1977 and Programme of Centenary Celebrations, Unley SA, 1977

Notes:
1. Strictly speaking there was no such thing as the 'First AIF'. The term is often used unofficially to distinguish the Australian Imperial Force of the First World War from the Second AIF raised to fight in World War 2.

2. The colour patch scheme was first introduced into the AIF in March 1915, just in time for the initial Gallipoli landings. The 2nd Division received its patches in August 1915, and gradually the scheme was expanded to include the whole AIF.