What is the solution to blue smoke in diesel engines?

Blue smoke indicates that it's running too rich. You have to adjust the amount of fuel being injected into the engine.

If is turbo diesel turbo is leaking oil into combustion chambers.

Blue smoke from either diesel or petrol engine indicates burning oil. Normally caused by failure of oil rings on piston.However,could be caused by other reasons such as valve stem seals worn.

I'm not much of an Diesel Mechanic but with the little information provided, I believe you are experiencing oil mixing in with your gas when it combust. this is caused by 1 of two things, if it is an older truck, your piston rings might be going out and letting oil seep into you combustion chamber and burning when the gas burns (cost more money to fix), or it could be that your "drain" back holes in the engine is clogged and oil is seeping into the valves thus in turns seep into the combustion chamber and you just need to clean it. you can do this by removing the valve cover and cleaning those holes.

worn piston rings or valve stems