Yep, sweet blue will show up even when it's "invisible" but you have to get the right angle of light on it. It's thin, and wispy, and almost invisible. It takes my WSM anywhere from half an hour to an hour to get my fire burning that clean. Depending on air intakes, fuel amount, etc. etc.
When it's invisible, that's when it's blue. The reason thin blue smoke is so hard to do more than talk about is by the time you can see it, where you REALLY want it, a camera is hard pressed to capture it.
The Life of the Knife is Ended By! The Wife.