Run into a weird bug in the process of repaining the map brown with Tecumseh; Ben Franklin and Catherine both settled low quality cities between mine, so when I want to war, I decided to raze them both and settle on the river instead. I'm not sure on the exact sequence of events as I wasn't keeping a close eye, but it looks like they either vanished on the same turn, or one turn apart. The bottom of the two relinquished its tiles correctly, but the tiles that belonged to the top one are still showing red, several turns after it went: