hahaha
turned out to be that photo was taken long time ago...
http://www.flickr.com/photos/46405720@N08/8581117724/ --> Christophe Choo's wife flickr account and the date stated there was january 30 2012, there's a pic of ayu and the wife with the same outfit she was wearing with christophe.
that means ayu doesn't change her hair color at all lol....