1999 Chevy Lumina car wont start

By grey, do you mean kind of blue-ish?
If so, there's probably oil leaking and reaching your combustion chamber.
Check your level of oil.
Some causes include worn piston rings, worn cylinders, worn valve guide or valve guide seals.

If the smoke is more like black, you're car is running on a rich mixture (too much gas in your ratio). This could be a leaky fuel injector, or maybe a clogged air filter.
Remove and inspect a spark plug to see if it's wet. Also, check your air filter.

Is your check engine light on?