Why do you get smoke from a diesel generator engine?
Even when not visible, smoke from a diesel engine is present. When you can't see it, that is a good sign that everything in the engine is healthy.it means the engine is combusting the fuel well and there are fuel particles of soot or other contamination in the exhaust gasses leaving the engine.
Smoke of any color is generally bad and should be investigated. You might see a little white smoke at startup which is normal in most cases. Smoke is a sign that something is in the exhaust gas.
What colour should the smoke be?
In a modern diesel engine, with the emissions regulations so tight the exhaust gas will be clear. this shows that the exhaust gas is free from any contamination such as un-burnt fuel, soot and water vapour. All these things show that something is undesirable is happening inside the engine as the fuel combusts.
Soot is a sign that the engine has too much fuel in the cylinder compared to the air it needs - this can be for all sorts of reasons. A lack of air in the cylinder will result in black smoke from your generator. It shows that combustion has happened, but the fuel has not completed its combustion. White smoke from the generator in contract shows there is a timing issue, or the compression ratio is bad. It shows the fuel is not really being burnt in the cylinders. Oil being burnt in the cylinders is indicated by blue smoke.
Remember you could have just one cylinder with a problem and all the others may be fine - you will still get a lot of coloured smoke.