[W126 Coupe] smoke on start up?

[Shayegan, Richard]

For a long time now (5 years or so) I've gotten a puff of black smoke
out of the tailpipe when I cold (or cool) start the car. I basically
ignored because last time I had the car in the shop, I showed the guy
(he was replacing a leaky fuel line while I was on the road, but he was
a good mechanic at a good dealer MB of Alexandria) and he said it's just
age and not to worry about it. Well today when I cold started it I
noticed the smoke looked like it might have been bluish. Cool starts
still only do black smoke, and once started the car is fine (no smoke
even at WOT, I'm getting good times for a 380, and it idles and runs
like glass even with busted motor mounts and my starting problem has
gone away, I guess I was too lean). What does this mean? I mean, clearly
it means some seal is on it's way, but which seal would only burn oil on
cold start (oil level is exactly where it is when I changed the oil 2000
miles ago) and what's the reason behind my puff of black smoke on cool
starts?
Thanks,
Richard