Tim,
The books that I have show the paint to be British Paints Signal Red BS537 BS381, NSN 8010-66-072-6868.
I think this converts to an Aussie code of R13, if you go to an automotive paint shop and ask for R13 see what happens.
I looked into the colour for my Fire Trucks and it was a while ago and I can't remember if this code is correct, I will check tomorrow.
Peter