Electrochromic thin films of metallo-supramolecular polyelectrolytes based on Fe(OAc)2 and 1,4-bis(2,2':6',2″-terpyridin-4'-yl)benzene are readily prepared by layer-by-layer (LbL) deposition or dip-coating on transparent conducting electrode surfaces. By applying a potential, we can switch the color of the films from blue to colorless. Because of the strong absorption and the fast switching speed, the color change can be observed with the eye. The devices show reversible switching and cycle stability.