Blue smoke is because oil is leaking into exhaust somewhere between the cylinders to the turbo charger. Find the oil leak. What engine, what age, and how many miles? Black smoke, FUEL, Blue smoke, OIL, White smoke, COOLANT. Very heavy billowing Black smoke, FAILED TURBO. Very heavy billowing White smoke, FAILED HEAD or HEAD Gasket. I've also seen Brown smoke which is failing EGR system.