The occasional white backgrounds are one of the things that bug me about the color volumes. It's this mix of full color and just "color elements on white" that makes scenes start to feel anemic. When it's all black and white there's no dissonance, a white background doesn't really seem any different, cause everything's white. It's just a way to emphasize the foreground.
A lot of the color pages really do look fantastic, but like that one up there with Akainu's lava punch is an example of a page that bugs me with its white bits. Feels kinda unfinished, feels like they're coloring something that wasn't built for color. Which, well, they are.
Now if every page looked as good as the actual Oda-colored color spreads we'd be in business. But as-is it's kinda so-so for me.