I would have thought with the work put into the Monaro Bill would have raced it for longer. Did you find any information on Denis Hamill who bought the Monaro from Bill Minty?.
Trade me is a good place to buy Monaro parts. I have bought a few Monaro parts here including a mint condition Bonnet.
John, printing inks have what is called a PMS code, and paint has a paint code. If you take that decal to a good automotive paint retailer, they can scan it and mix the closest possible colours to it. That is your only real option.
I have the ex Laffite Gitanes Ralt RT4 and when I was looking for paint colours I went to an enthusiastic paint supplier ( Motorsport Fan ) and he went back to the old formulas and hunted through them and found that it was painted in Gitanes corporate colours, maybe the Cambridge colours are corporate colours as well.