blue smoke could be oil, but then diesel is a fuel oil, so it could be unburnt fuel just as easily as oil.
it could be your turbo bearings are leaking, it could be that the oil breather is chucking a lot of oil through, it could even be the injectors leaking a bit overnight or could just be unburnt fuel for the first few seconds of the day.
mine can be a bit smokey at startup when cold, personally, I just ignore it and carry on.
if you were leaking oil and it was a major problem you'd see smoke constantly throughout your journey, not just when you start it. providing she is burning well and smoke free 99,9% of the time I'd not worry about it!
1999 156 1.8TS Sport Pack 3
2001 166 3.0 V6 24V Super
2003 156 GTA 3.2 V6 24V
2005 156 1.9 JTDM-Jet Sport
2008 159 1.9 JTDM Lusso
1997 GTV 2.0TS Lusso
2001 147 1.6TS Lusso