Hi Richard, I've always assumed NZ was like Aus. in its banning of caudates in the pet trade except axolotls. Glad to see that's not so.
Red spots and streaks on the body are not uncommon in orientalis. I have individuals with red spots above the hips, on the head, and on the upper forelegs. It would appear that the variation you're seeing is just natural variation among orientalis at this point. I don't think anyone has done any studies yet to see if the variation among the newts currently recognized as C. orientalis are due to subspecies or new species. It certainly could prove to be so in the future.
As for the vocalization...newts do not vocalize intentionally. That is, there is no reproductive or social use for it. I've never heard of such a thing, and I think you may just be hearing them when they gulp/expell air.