@Operaphile --That sounds perfectly reasonable to me.
Even Shure reps are confused. I just got off the phone with one who told me “no, the U.S. version is tuned like the clear and bronze”. I offered resistance to that notion and was switched to someone (presumably) more knowledgeable on the matter and that individual told me the red earpieces indicates that there is indeed a different acoustic filter in the nozzle (no matter where it is sold). So, there you have it.
I auditioned the Red 535 in InMotion and I did not hear a difference. If there is a difference, it is not a blatantly obvious one. I did have the treble turned up high on Poweramp (as I normally do for my clear 535) which may have mitigated the difference. But whatever, I'm way over it and waiting for the SE846.
As for the W4, I can hear a difference in its treble vs the 535. I can also hear a difference in the mid-vocals where the 535 wins (but it is early yet in the comparison, so things may change). The 535 also wins in visceral bass. As with the IQ, UE900, SM64 and now W4,--the 535 seems to shine in foreground sounds where the others win in background clarity (but again, it's early with the W4....).