I would think that the color spec maybe different for Nissan units produced in the States vs those produced for the UK is probably different. My experience with Mitsubishi when they went to that "Kermit the Frog" green (aka Jewel Green) - US suppliers had a real hard time exact matching the spec of Japan painted units due to difference in paint methods.
But as that oldies song goes "that was yesterday and yesterday is gone" - maybe they found a fix.