Tony
Well it isn't Frankfurter...what a bloody disgrace! Did you play there before the changes?
I think in comparison with the other architects from that era Colt has done reasonably well, until recently when clubs have caught the redo bug, such as:
Eden (what a hatchet job)
Dublin (most greens dug up and USGA'd)
Hoylake
Frankfurter
Hilversum
Belvoir Park
Camberley
Royal Wimbledon
...and now that bastion of great design, Ernie Els, is going to dig up and "modernise" the greens on the Burma Road.
Portrush is probably the best preserved, there were changes to a couple of holes but Colt and Co did the design work. St Germain is a good choice too, some major revisions but very early on, with nothing much since (2nd green needs fixing). Swinley and SGH aren't much different other that the poor bunker work and Wentworth East as well. Swinley had some changes early on but I'm pretty sure these were under Colt's supervision (his favourite course after all); there were also some minor tweaks by a misguided secretary (softened a green or two) in last 15 years. Addington?
I agree Toronto is a good choice, although Alison made a couple of significant changes and Watson altered a green or two (I actually like his 16th green and the 2nd isn't bad either)
Hidden gems like Harborne, Whittington Heath, Effingham, Brancepeth, Prestbury, Brokenhurst, Trevose, St Mellons, De Pan, Eindhoven... all pretty close to as designed.