'purple codices'

'the few books from the sixth century that do survive are among the most carefully and expensively executed of any period. . . .

The sorts of books that were decorated and illustrated with images at this time were almost exclusively biblical'especially the Gospels, but also for some reason the Book of Genesis. Books were written by hand, by highly skilled calligraphers, on the specially treated animal skin known as parchment. . . . The most costly and ostentatious treatment a book could receive . . . was for it to be written in letters of silver or gold on parchment that had been dyed with the purpura dyestuff usually employed for textiles, and at this period reserved for imperial use. These books are generally referred to as 'purple codices' (Latin codex meaning book, as distinct from roll or scroll), which is misleading if we imagine that this describes a particular colour of parchment, for the purpura dye can produce a wide range of intense tones between a deep bue and deep red. . . . The pages of these books never equate with our modern notion of the single colour 'purple'.'

'John Lowden, Early Christian & Byzantine Art, 1997.