No, I appreciate you mentioning it - it wouldn't have crossed my mind as a cause! (Let's face it, the state I got it in, who would have thought it'd been even in the same room as a dishwasher? :lol: ) I'd just put it down to either a purposeful quirky finish, or a flaw somewhow when it was made.
It's very peculiar, because if it was metal, it would look very much like someone had taken a blowtorch to it - it's mostly focused at the front of the rim, on the right side, and it spans out from blue at the centre into bright purple and then a burnt reddy orange and then fades into the normal glass colour. I wish I could photograph it, but my camera refuses.