The word of the day is foxed:

Of the leaves of books, also of timber; Discoloured by decay; stained with brownish-yellow spots. (OED)


"News of the world lay in the rain.
Maple leaves fell, pre-foxed,
as if stored for decades on library shelves."

 - William Logan, "Mysteries of the Armchair", 6 December 2010 The New Yorker