I have been saying it for five long years now- She’s going to Sea in PLAN colours!
Yes it is smoke coming from the stack, this would mean that something is working inside- now I wonder, considering the amount of cooling units on the above pics arranged across the decks, I wonder if they haven’t tapped these into the stack below in some kind of ad-hoc ventilation with respraying the hanger area, to help dry it out quicker! We did something similar when I was in the navy with STS Young Endeavour.