This is all fascinating. But the big problem with comparing photos to discuss a color's true value can be wildly misleading. You just can't determine the real color this way. From lighting, to film stock, to print, to web colors, these pics have gone through a slew of color distortions that simply cannot give you any true way to nail down the correct color outside of pure guesswork. Just because a photo of an original helmet is shot in sunlight doesn't mean you can paint something and shoot it in sunlight and match that color photo-wise and have actually accomplished a real match outside of the photo. For starters, film stock alone has a huge impact on color response, especially if you are now using a digital camera with CCD's, not color film negative like what was used in the original production photos. Even digital photos of the exhibits have similar issues with CCD's.
Obviously even if we had the original paint list, though, getting a match is still difficult because weathering makes a huge difference in the final color. Maybe the current owner of the pp2 could take mercy on us and offer up a photo of the bucket next to a color card. (Did anyone who took pics at the exhibits ever use a color card for at least one shot???)
In the meantime, I do think you guys are doing as good a job as can be expected under the circumstances and I look forward to seeing what comes of it. I am sure there are going to be some awesome PP2's come as a result of this thread.