Yes, I had two teas today. One in the morning (right) and one at night (left). Both are baozhongs, but one (left) is a 2007 baozhong I got from Taiwan. The one on the right is a 1980s baozhong, the leftover of the sample from Red Blossoms.
Obviously, colours change over time as the leaves become more oxidized. Since oolongs are generally not left to open air, at least baozhongs (baozhongs get sour fairly easily, it seems) the process probably takes place as whatever compound ages…. although I’m not sure how it ages. Does it react with the little bits of oxygen available to it in the air that it does have contact with? Are there enzymes remaining in the tea that are not killed 100%? I don’t really know. I do know that the tea generally acquires a sort of darjeeling-esque taste. Don’t ask me why.
They also get more broken over time. Obviously, normal wear and tear happens. However, it also happens during reroastings. Now, this Red Blossom tea was suposedly never reroasted, but nobody said anything about the strength of its original roasting, or that it could have been blended (I see evidence of that). Anytime somebody sticks their hand in there to mix up the leaves, some get broken.
Now, these days the oolongs are all rolled very tightly, and so breaking is not as likely to happen. However, that’s also a hint of age – if a gaoshan oolong is only loosely rolled, chances of it being old is higher than a very tightly rolled one. If you’re buying an “aged” tieguanyin from the mainland that is strongly roasted and tightly rolled… buyer beware.
None of these, of course, are foolproof in any way. These are just quick rule of thumbs I’ve learned over time by poking my head into many shops and buying some tuitions along the way, but I think they generally are true… and worth keeping in mind when trying to buy older oolongs.