Аннотация:At epochs of optical eclipse (Min I, orbital phases 0.97-0.03) the U magnitude and U-B color of HZ Her vary (0.3m amplitude) on time scales of months and years. The long-term U-B variability correlates with the turn-on epochs of the Her X-1 source, and thereby with the fluctuations in the length of the 35d cycle and in the X-ray pulsar period P_pul: low U brightness is accompanied by a lengthening of P_pul whereby the propeller effect should increase the amount of gas in the binary system. Cool (6000-7000 K) gas issuing from the hot corona above the outer accretion-disk ring may collect near the optical component on the side away from the neutron star, perhaps causing the variations observed.