It is also reasonable to think that DEC did a run of
VT100oids with green tubes.
Or a repair job, come to think about it. I pulled a half pallet of new
National 12" tubes out of New Jersey a few months ago - a mix of
white, amber, and green - destined for replacements in terminals. The
electronics does not care about the phosphor color. And maybe the
repair depot techs did not care either.
--
Will