Hi.  Just sent a post to Lisette, but then decided that I'm kind of
curious about what other people know about this thing in case I'm missing
something, so here's the text of my post to her.
 
To the best of my knowledge, the only explicit reference to a "rainbow
bridge" in mythology/sacred texts is to Bifrost, the rainbow bridge that
connects Midgard (the earthly realm) to Asgard (the realm of the gods)
in Norse mythology, and which is guarded by Heimdall, a sort of
guardian/herald figure.  I'm not up on that particular motif in other
mythologies, though, and I wouldn't be surprised if it pops up elsewhere.
If I happen to have a motif index nearby in the next couple of days and can
remember, I'll have a look-see. =)   Anyway, sorry to bother you if your
interest has waned, and have whatever sort of day you're inclined to have.
 
Otter Driver (and ferret Rorty)
[Posted in FML issue 2618]