Long Term Variability and Color Index Variability of 6 Blazar Objects

Lots of quasi-simultaneous observations for 6 Blazar objects over 15 years were processed and analyzed in this paper. The curves of variability and color index variability were obtained. The variabilties of color indices were analyzed intensively. According to the correlation analysis between the color indices and the magnitudes, we concluded that the variability of Blazar objects contained the long term achromatic variability and chromatic short flares by comparing the light curves and the curves of color index variability. It is indicated that the shock-in-jet model modulated by geometrical effect may be the physical mechanism for Blazar variability based on the difference for the color variability.