Hi there,
My ancient living rellies have been brain storming, led by one who is a retired Archivist, started out at the Archives Office when it was part of NSW Library on Macquarie St, and went with it to Kingswood and then was seconded to Canberra to the NAA.
Using the naa.gov.au record search option, and just using the keyword option, enter your chap's NX number. (only the number, not his name/s, ABSOLUTELY NOTHING ELSE). Notice that there's TWO options - a pdf set and a digitised set. The brilliant pink of the pdf set is NOT near as brilliant pink on the digitised set, but that initial form is definitely on pink paper.
So, go back to the keyword search option, and change the NX numbers you are searching for... use the same first FOUR digits after the NX, but vary the final digit, some higher and some lower...
Some of these have been digitised, but even reading the index info, for the ones not yet digitised, there's every reason to believe that Paddington NSW recruitment was using PINK attestation forms in early 1942.... Paddington is where Victoria Barracks has been located ever since the mid 1840s..

There's those PINK forms.

.... one chap was E.C. 1st Reserve M.T ....

JM