Ironically I have been pondering what color reader bezel would work best...for my K1, well, nothing will make the display look better. Soon as the warranty is done I am going to crack the case and buy a few cans of Krylon to see that works best but I doubt anything can really save that gen1 display. Gen2's are not much better...
If I had to ponder a guess, I have been thinking in terms of print books...a nice dark brown that is not too dark but also not too red (mahogany might be too far) would be the most aesthetically pleasing to me...I still would buy one with that Asus bamboo case because, well, that is kinda silly.
I am actually surprised I like the white on the K1 we have, still hate the display but the bezel is not a distraction. Greens and blues are good too because of how our eyes/brain respond to them. Blue is not called "the seducer of the mind" for no reason. It is a color that people tend to subconsciously associate with relaxation. I would find a non-earth tone color palette distracting, save for white. And I thing we are just conditioned to black for laptops.
BTW, if any of your devices are going to come with a glossy display, you should be flogged nekkid at sunrise, but otherwise there is a very inexpensive fix on the consumer end. It is using Boxwave Clear Touch Anti-Glare. But never having used on on a non-backlighted display, I have no idea how significant the light loss will be:
http://www.boxwave.com/products/cleartouch/index.htm
But for your Pixel Qi based reader it might be a way to reduce the layers by using a glossy display for those who want one yet allow the addition of a protector from Boxwave. Of course you can go in the other direction as well by having a matte finish display and using the glossy display protector from Boxwave which has virtually zero light loss. I use the Anti-glare on my Nokia N800 and love it. The thing actually improves the touch screen response on mine.