I second Tony's comments about Protec; it is grrreat paint. After countless attempts to remove it from my garage floor (even with some serious chemicals) most has stayed put. Petrol: no worries, it is over-sprayed onto one of my Gerry Cans (don't ask) and doesn't wash off.
I noticed it is a slight bit less dark than the WWII green, which, to 'correct' the green you need to add a little brown. (sorry I had to say...) If you want a good paint match to that on a Blitz, then the chassis (that's Aussie for Frame) rails in the engine bay are close & unfaded if they are covered with grease & crud you can find a bit of painted section which will be unaffected by sunlight etc.... Also when you separate the front cowl from the cabin, the paint in there is the original stuff unless you or someone else has re-painted.
You will notice, if you put a little dab next to the original, let it dry and then check it out in a few days, you can see the protec is a bit lighter... In my honest opinion I use it straight from the tin as no-one has perfect colour vision, and NO truck had perfect paint. (I have re-introduced the factory runs into my paintwork intentionally.. Not like some who have added them in haste
I would NOT suggest people change the tint themselves unless they are experienced painters otherwise you will have a browny greeny mixed paint
Probably the way they were new (200 shades of Olive drab & Green).
Oh and inside ammunition boxes provides a good guide to how much variation there was... I have a few 1950's boxes of varying shades...
Ian