Black smoke - too rich
White that disappears (it evaporates very quickly) is
only on watercooled engines & can mean a bad head gasket or other way coolant is getting into 1 or more combustion chambers. So Andrew has it partly right.
White to Bluish-white smoke usually means oil is getting into the combustion chamber - usually past the rings, and that can happen then go away in a motor that sits or when very cold & they shrink until warmed up (I mean Alaska & Dakotas cold).
However IMHO, you need to watch it & if it keeps up or gets worse, you'll need to get it rebuilt. When mine went at about 130k it blew out a huge cloud of white/bluish smoke as I decelerated down an off-ramp from the freeway, so I knew it was time! Same thing happened a couple of years ago in our Westy, & we needed a top end done.
You could do a compression check to see if 1 or more cylinders are more than 10-15+% below the others, which would tell you where the bypass is occurring. when it's really bad, you'll notice a loss of power.