Exhaust

Light colored smoke out the exhaust is normal until the engine warms up, especially noticeable on cold mornings dense air. Blueish/gray smoke is a sign an engine is "burning oil", excessive black smoke would be a sign an engine is running to rich/too much fuel is entering the engine. White steam perhaps noticed with a slightly sweet odor from the exhaust, rough engine running, over heating and or coolant loss would be a sign of a blown or mildly blown head gasket. Black smoke is too much fuel , blue gray is oil smoke hard to say which you have without seeing the smoke first hand. A cylinder leakage test would show if the piston rings or bore were worn.