Hmm....there's some mixed info going on around here.
I have been to three or four Johnnie Walker promotion nights and spent a lot of time talking with their brand ambassadors. I don't claim to be infallible on this, but I'm reasonably confident that the following is correct:
Heart of JW Red - Cardhu
Heart of JW Black - Cardhu
Heart of JW Gold - Royal Lochnager
The "heart" of JW Blue and Green has never been pushed, promoted, or stated.
All of the promotion nights pushed Cardhu and it was made very clear that it was the heart of the Red and Black blends. If the heart of JW Black was Talisker, it would be a very, very different tasting whisky. You can certainly taste a bit of "zing" on the palate that is Talisker's contribution to the blend, but it's a top note only.
And yes, the story does go that JW Blue contains whisky that is in the order of 60 years old.
Now here's a trivia question.....who knows anything about Johnnie Walker "Swing"?