White puffs of smoke when starting a car with a cold engine on a cool, damp morning are normal. They are due to water condensation in the exhaust system and engine. As the condensation warms, it creates a white vapor similar in nature to that formed by human breath on a cold day. It disappears as soon as the condensation evaporates.
If the white puffs continue after the vehicle reaches normal operating temperature, they indicate a more serious problem. While the clouds are still likely water vapor, the source is no longer condensation. Instead, the vehicle is likely to have a blown head gasket or warped cylinder head. Drivers should have a mechanic check this problem.
If the white cloud persists, there is a good chance that coolant is leaking into the combustion chamber through a cracked head gasket or other route. In this case the burned coolant is causing the white cloud.
Black smoke indicates a fuel mix that is too rich. A stuck choke causes this problem on carbureted vehicles. It is time for a tuneup. Black smoke is a sign the car is wasting fuel and creating pollution.
Blue smoke is due to oil burning in the cylinders of the car. This is the most serious of the three conditions, according to the Orlando Sentinel. Engines producing bluish smoke often require major overhauls.