The color is going to always vary based on lighting and what the background is, but the 4G iPods are supposed to have a blue backlight. I've heard the light referred to purplish blue, and based on your picture I'd have to agree. Of course, under different lighting and not held in front of an aqua blue screen it probably would look bluer.
edit: Check out how different the backlight looks in this picture compared to yours. In this photo I think it looks more like a blueish white, but is obviously not the same white as used in the 3G iPod. (Photo credit to ipodlounge.com, by the way.)