In pre-modern Japan reclaimed paper was made using the pulp from previously used paper. The ink gave it a greyish color, and sometimes the palimpsests of previous characters would show through.
Reclaimed paper was used for imperial decrees like the one above, from Kyoto, where the color conveyed sacredness and majesty. And it was used to print sutras, where it was imbued with the spirit of the person who wrote on it previously. Using kankonshi 還魂紙 (paper that causes the spirit of the deceased to return) for sutras, which never got recycled, was a way to ensure a long life. Though it also sounds like it could be a way to make your books haunted.
Anyway, if your karma needs a boost from protecting a kankonshi sutra, Jonathan A. Hill has an extremely rare example from 13th century Nara.
image: an imperial decree on reclaimed paper, c 1333 CE, from the Toji Hyakugo Monjo