Probably the liveliest simile for whiteness I’ve come across, though I have highlighted others, less earthy.

‘Daniel, you’re as white as a nun’s buttock.  Are you all right?’

See also our celebration of this book, complete with a mosaic of illustrated quotations and metaphors.

Source: Carlos Ruiz Zafón, The Shadow of the Wind, trans. Lucia Graves (London: Phoenix, 2012), p. 91