Thanks for the feedback. That the berets are reading as red shows there is quite a bad colorcast on the image - the color is a reddish brown.
The M10s were part of the artillery units.
In the Union Defence Force (as it was then), in many cases the beret colours pointed to the history and origins of the units. Armour/cavalry regiments = Black, Field artillery = (dark) Blue, Infantry = Green, etc. (There were exceptions, so the Imperial Light Horse, for example, despite being a mechanized infantry regiment in Italy, wore the black beret which pointed to their cavalry origins). I couldn't find a color image of the 1/11th, so worked backwards from current regiments and compared them to other support regiments. The modern antecedents of the 1/11 use a red-brown, so it was a toss-up between blue (field artillery) and red-brown (some support regiments). Local military historians that I asked were not sure, but agreed the density of the berets in the black and white images looked more like red-brown than blue. The sappers and other B-echelon forces had the khaki beret, as far as I am aware. Short version: I am ready to be proved wrong...
As for the variation in tank color, the South African division showed a huge variation in vehicle color in Italy , with General Orders re: painting applied on an "as and when possible" basis. They were under command of the US 5th Army towards the end of the war, (a bit out of sight of the British General Staff) so a mix of Olive Drab and SCC 15 was evident, as well as the Light Mud/Blue Black "Italian pattern", and even the desert "Light Stone" (with various disruptors) and "UDF Olive Green" (the color used in East Africa, home front and Madagascar).