A flexible electrochromic device is disclosed, the device including a flexible substrate with at least one electrically conductive surface, and an electrochromic layer comprising particles of water-insoluble metal ferrocyanide with an average particle size less than about one micron, and polymer, the electrochromic layer deposited on a conductive surface of the flexible substrate, wherein the device is capable of being deformed and returned to "flatness" in an undamaged state.