Were the exhaust stacks on the Henschel KT bare metal?

I would assume they were painted with the rest of the tank; so no, I would not leave them bare metal.

They are not made out of rust either

I don't know for sure, but I bet if they had armored steel, grey cast iron, ductile cast iron, chromed bores; they also used galvanized steel.

I am not directing this at you, but I seem to be on the losing side of making exhausts soooooo bright red. A little for flare here and there, or a really old tank maybe. I am sure the paint would turn all sorts of nasty colors. But for a king tiger whose life would be ~1 to 5 months on average, I wouldn't expect fiesta red mufflers.

I believe they are done rusty because the paint can't hold up to the temperature of the exhaust.

Considering the shortage of resources the tank's armor would have been the priority so i would guess any materials of decent quality would not have been wasted on the exhausts. They would of know that these tanks wouId not have a long lifespan so I guess the exhausts would of been made of whatever was let over .

Guess the thing to remember is they got extermely hot. Combine constant heating and cooling and the expansion and contraction of the metal with moisture and you have perfect conditions for rust. Any paint coating would not last long.