In the 80's and early 90's clear and amber Fire Ball II lenses were everywhere and if I would've known how rare they would become I would have acquired loads of them because in those days they were both plentiful and cheap but that's the way it always works.
We only used red lenses in the
FD but for some unknown reason there were a number of amber, clear and green Fire Ball II lenses in our supply lockup. Because of their colors they were never used and sat there for years but at some point I'm sure someone grabbed them but back then there was nothing special about those particular colors