Thanks, seems like Fentek call them 'off-white'.
And Unicomp (why didn't I think of them?!) list this:

Looks toothpaste-advert-white rather than off-white though. :-
'D
They also, IIRC, helped iMav out with some custom keys. So an email to them might not be a waste of time :-)
It might seem like I'm being fussy - and I am! But if I can't have them match the letter keys, I think I'd rather just keep them grey.
lowpoly - re. 'exactly those keys' - if you mean the tab and backtab that I've used as home and end, then no, I'd be happy with 'home' and 'end' legends.