Scott - my understanding is that you are indeed correct. The colour was due to the mixture used on the funnels during the early-days. The black top was actually originally caused by this mixture becoming dirty / burnt by the heat and soot while the original 'black bands' were the connection mechanism between the funnel sections.
After the Cunard-White Star merger, the White Star liners retained their buff funnel livery. This was most notable with
Britannic and
Georgic which retained their unique identity long after White Star disappeared. In fact,
Britannic was the last of the White Star Liners, retaining her original colours until 1960.
http://www.chriscunard.com/archives3.htm#Britannichttp://www.chriscunard.com/archives3.htm#MV_GeorgicQE2 - as you say, was the start of an exception to the Cunard funnel colour rule. Her scoop sported the "Cunard Red" while the rest of her funnel was white & black. Similarly we saw white funnels aboard
Cunard Ambassador, Adventurer and
Countess until the
Countess appeared in traditional livery.
QE2 followed after the Falklands campaign.
Interestingly to note is I've heard that
QM2 actually was painted with the wrong shade of Cunard red and only last year during her refurbishment in Hamburg was she treated to the traditional Cunard red. During my recent voyage aboard her funnel is looking magnificent in the red/orange we're all so fond of - but indeed looking back at photographs from 2004 and 2007 it does appear to be a darker shade to
QE2 or those that came before her.