non-optimal choice of color for "blank" images?

[Hank Bromley]

See Bug 690208 filed against ia-techsupport. Scancenter staff saw what appeared to be a blank white page after the book cover and asked where it came from.

The previous version of the BookReader used more of a rust or chestnut color for the empty space opposite first/last pages in 2up mode, which looked sort of like an inside cover. The new version apparently uses white, which is probably not the best choice, as it does look like another (blank) sheet of paper. How about the same gray as the overall background?

(I see the image is actually called transparent.png, so maybe the gray background was indeed what was intended, and some intermediate opaque layer is blocking it, yielding the white page?)