Speaking of bug reports, I found a rare one.
See the eight-province red-yellow maskling tribe? The correct answer is "no", as that's actually two tribes with the same culture, same primary color, and same secondary color. They even have similar names (three-province Bloodcrusher Clan in the east, five-province Bloodcutter Folk in the west).
Yes, the odds of a match like this are very low, but obviously it can happen! ;)