Art,
There is no official color for the knife, other than the fact that it was a dark olive drab. The Studio Creations website gets it exactly right. It is darker than it looks in pictures, so get the darkest OD you can (and one that has more of a grey base than the yellow base that some ODs have).
There are very few OFFICIAL colors for the props in this movie. One of the things that makes color matching more difficult is that the costumes and associated props were made in both the UK and South Africa (well, not the belt items, aside from the buckles, they were made in South Africa only). For the UK items, we have a bit more consistency (we know Goldfinger was used for the shoulders and we have a production paint chip for the helmet red that matches MOST of the helmets). Once things got to South Africa, it gets a little murky. Apparently there were times when they just grabbed any old can of paint off their shelf that looked decent (this was a low budget movie, after all).
There are some items on the suit that we have matched by eye to pantone color swatches (in person, in natural light), so that might be as good as it gets for those. We did not match a pantone for the knife however (we had limited time), so dark grey-based OD is the best advice we can give.
Back to the red on the UK helmets - it was custom-mixed. I have a paint chip provided by production and I was able to get a paint specialty place to match it pretty perfectly. They are available for sale, but they only come in a box of four cans. But it's a high quality spray paint and just one can could probably do several helmets. If people wanted to share a box with some friends, it would make it more affordable. Because it ain't cheap - $153 for a box of four cans shipped within the US (not available for overseas shipping).
If there is interest in it, people could PM me. Or I guess I could start a thread in the junkyard about it. It ships direct from the factory, but people have to buy it through me at the moment.
I'm working on possibly getting an exact match for the knee, elbow, and toe color via a production paint chip as well, but that's in the early stages (would be cheaper though since that's a simple liquid paint and not an aerosol can).
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PS most of the knives I've seen look darker OD in person than that pic you just posted above from the stunt uni. But that color is not far off and would probably be good enough.
PPS I just went back a page and saw the knife you painted. That looks pretty close. And in answer to your question about painted screws, all of the knives I've seen have had painted screws (including the large screw at the base of the blade). I suspect there was only one real knife on set, and it was the one used for that closeup. It's too hard to tell how that one was painted though.