Truck cold start smoke

What colour smoke, white, grey, blue or thick black?

white is water vapour (nothing to worry about), blue means there is oil getting into the system somewhere, grey could be oil too, faulty PCV if it has one or transmission fluid getting into the engine from a leak (bit less common) or turbo issues, black usually means too much fuel, in a diesel a clogged DPF if it has one, each colour smoke could indicate many things.

Depends on what engine is in it diesel or petrol, I would usually check air filters, injectors if you can and any visual issues like leaks you can see in the engine bay, if its a diesel especially give it a blast down the road when its up to temp and get the revs up and check in the mirror for any smoke coming out when your foot is down.

depending on the mileage on the car and how its been driven and maintained could also indicate why its there.