Long since lost track of numbers...
In my campaign, dragons have been around for all of history (and in fact date back fifty million years before that). Their civilisation works on a different time scale to ours, and because dragons are fiercely individualistic, they normally live out their lives without interacting with their peers. And their lives are long... the one dragon you can see on my website proclaims he was ancient when the Pyramids were built, and he was probably around when humans first crawled out of the trees. (Who do you think burned down the forest in the first place?)
Dragons as mortals percieve them are pretty much straight D&D. A dragon rules what it surveys with an iron fist, but rarely uses that fist because it has the patience to wait. Dragons are overlords, and anyone who knows a dragon knows that they're not to be trifled with. Even metallic dragons are so far beyond humans that they would probably crush you if you got uppity. (It's like dogs. A nice guy will put a dog down if it starts biting people. A nasty guy will see a dog in his yard and check to see if his shotgun is loaded.)
Then again, nobody has ever seen enough dragons to classify them by colour. Case in point: There have been precisely 4 dragons in this campaign so far, and they all look completely different, AND they've only been seen collectively by a small group of world-trotting adventurers.
Dragons are powerful magic-users and fiercely intelligent. They have doubtless done everything humans have, and done it better, millions of years ago... and that's dragons without classes! A draconian hero is something I haven't even considered using... yet.
I personally love dragons. LOVE them. And I think this approach reflects some of that...