http://www.muji.us/store/stationery/notebooks/recycled-paper...
The paper is a nicely aged light brown with a gradient towards the edge now.
https://dl.dropboxusercontent.com/u/8403291/muji-b5-2000-cro...
Snap does not show the full gradient but you get the idea. Pages flexible, no cracking or anything.
Oddly enough, the pages in the squared version of the notebook are still bright white, no sign of ageing at all.
http://www.muji.us/store/stationery/notebooks/recycled-paper...