Unburnt motor oil, and unburnt diesel fuel is blue. Properly burn them both and you won't see anything. Burn too much of it and its black, mostly from soot. Did you ever see a diesel tractor pull? My point was raw fuel coming out of a gasser is black, raw fuel coming out of a diesel is blue. And what vegetable oil looks like I don't know. I also think some of the smoke in the video is burning rubber.