I hadn't checked until now, but Color is definitely off a bit on my set. It is hard to tell from pictures, but I don't think it is as much of a difference as Chris is seeing. I was able to shuffle my stack of Rangers into the Provinces from my Base Cards, and separate them with no mistakes in less than 30 seconds only looking at the backs.
I don't think I would be able to tell without practicing just by looking at one card at a time. I don't think there are many situations during game play where I would notice without consciously trying to cheat.
Edit:
After spending a lot more time with the cards tonight trying to decide how many of them were offset significantly enough to request replacements, I've decided my set is probably very similar to Chris's. Sometimes when I looked at two cards side by side it seemed like it was barely different, but other times I would look down at them sitting next to the not-perfectly-centered Spy I was comparing them to and thought "man, those look like they are a very different color".
I emailed RGG tonight and inquired about the color difference in addition to the off center cards, so I will see what they say.