I just saw the Amazon Kindle and Nook Touch in the store, and the background is not very white neither! In fact, the background may be just as grey as the standard Jetbook/lite's!
So all this talk of grey JBC, but if you ask me, none of the e-ink screens look white!
I've done a sample from memory, on how e-ink compares to Jetbook. It's not 100% accurate, but from memory it looks pretty much like this:
That's how I saw it standard light;the brighter the outside light, the whiter the background white of the Jetbook becomes;the brighter the contrast becomes of the Jetbook.
On the Kindle, you're pretty close to a white background, the effect is less there.
In fact, you don't want to read the kindle under sunlight, as it'll burn your eyes.