Thanks Tim, yeah I've got to admit that it's a wee bit confusing.
As I mentioned earlier in my bucket thread, I've been using the images Star Raider posted up as my reference for painting and it appears that the drop box is as white as the rest of the armour, particularly noticeable in the image below;
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In this portion of the skin, enlarged for effect, the drop box (A) appears white and is used in the first pic.
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Then when you look at the TKC skin as a whole, it would be hard to suggest anything but white for the drop box.
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I want to paint my armour as accurately as possible, but as far as the drop boxes go, for the life of me, I just do not see them as grey.
The skin and the renders are pretty convincing to me, and seem to support white.