Digging more into this strange camera artifact problem I've been having, I decided to try uninstalling/reinstalling the Google Camera app. In this case, it means uninstalling any updates and and updating again from the Google Play store.
Uninstalling and reinstalling the update (2.5.052) didn't help things. The shifting is most visible with the red in the map on the book cover, but it's a global shift in the entire image.
Then I thought I'd just uninstall the updates and revert back to the built-in version of the camera app (2.4.018) to try that out. Much to my surprise, I got a perfect picture.
It's pretty reproducible too. With the latest update, the colour shift artifact is there. Back to the built-in version, it's gone. This is getting a little more interesting. Seems more a software issue now than hardware like I was starting to suspect earlier.