The effects of multiplicative colored noise and additive white noise on the mean first-passage time （MFPT） T+（xs1→xs2） and T-（xs2→xs1） of an optical bistable system are investigated. The approximate Fokker-Planck equation is obtained based on the Novikov theorem and the Fox approach. The expression of MFPT is obtained in the steepest-descent approximation. Numerical results show that （1） the multiplicative noise intensity Q and additive noise intensity D play the same roles in T+（xs1→xs2） but different roles in T-（xs1→xs2）;（2）T+（xs1→xs2）increases with the increase of the self-correlation time τ but decreases with the increase of the correlation intensity λ；（3）T-（xs2→xs1）decreases with τ increasing， but increases with λ increasing.