The variety of pages is pretty astounding, and it's going to be great fun. Here's a link with all of the links. And if you are on Twitter, here's another list. Colorers are encouraged to share their pages on all social media sites, using the #colorourcollections. I'm posting mine on Facebook and Instagram (I stay far far away from Twitter).
I jumped the gun, and have colored several pages already from books that were available early:
From the Biodiversity Heritage Library - they very helpfully provide coloring suggestions... heh...
From the New York Academy of Medicine coloring book.
From the Bodleian Library
There's no way I can keep up with all of the participants, but I'm going to snag as many of the pages as I can!
