green light question, not the cover though

[kjirstem]

Speculation about the greenish light on the Scholastic cover for HBP
has reminded me of a nagging question I've had for some time.  

When Harry's Gringotts vault is first opened a lot of green smoke
billows out. There is no mention of a similar effect with the vault
the Stone was in.  This seems strange to me and I've wondered if it
was significant at all, perhaps associated with the events at Godric's
Hollow.  I'm sure this has been discussed to death somewhere that I
can't locate, looked on the Lexicon and in Fantastic Posts, so I
thought it might be more appropriate to post here rather than on the
main list.  Does anyone know off-hand the whereabouts of previous
discussion? 

Thanks!
kjirstem