exhaust smoke explain white,blue,black-sinhala 

indicator that your engine is burning oil. This produces a foul burnt oil smell to all the cars behind you, and if you're one of those cars following someone who's burning oil, you're quickly reaching for the A/C recirculation button in your car to stave off the horrible smell.
Billowing black smoke is generally a sign that the fuel-air ratio in your engine is too rich. This means that the fuel injectors are either adding too much fuel or that the intake valves aren't letting enough air in.
White smoke from your exhaust almost always indicates a blown head gasket, and just like there is coolant mixed with your engine oil, there will also be engine oil mixed with your coolant.