An electrochromic assembly useful for rearview mirrors, windows, vehicle sunroofs, information displays, office partitions and other structures which allows prolonged coloration substantially indefinitely without voltage or concentration gradient induced color segregation. The assembly includes a pair of optically aligned, electrochromic devices defined by at least one transparent sheet, first and second layers of electrochromic material adjacent opposing surfaces of the sheet, the transmittance of said layers being variable when an electrical field is applied, and electrical conductors for applying such an electrical field. Electrical energy is switched alternately from one device to the other for short periods of time while the remaining device is alternately bleached. The switching can continue cyclically for any desired period. A reflective coating may be included to allow operation as a dimming mirror. Anti-reflection and index of refraction matching coatings may be included to enhance transmission. Electrical energy may also be applied to both devices simultaneously to provide a deeper level of coloration than is possible from either device alone.