having seen the SD at the MoM I can tell you it is definitely not white. It is a very lite gray color with thousands of scribed panels, some of which are a slightly darker - and I mean SLIGHYTly darker gray. when hit with the camera flash it sometimes appears white but under regular lights lite gray.
sure looks white to me, on the theatre screen, and just as with the TIE fighters in Chronicles, all the different lighting and photographic exposures make a hash of it.
I went with something like half insignia white and half Camoflage Grey on my kit, after first pre-shading things with black.
Thanks but this isn't actually a Star Destroyer model... You'll see by this weekend. Someone at SSM said the SW Chronicles says that they used matte white, but I think I'm going to go with either a lighter gray color or mix white and camo gray.