We examine \sim 10 years of photometric data and find that the black hole X-ray binary V4641 Sgr has two optical states , passive and active , during X-ray quiescence .
The passive state is dominated by ellipsoidal variations and is stable in the shape and variability of the light curve .
The active state is brighter and more variable .
Emission during the active state varies over the course of the orbital period and is redder than the companion star .
These optical/infrared states last for weeks or months .
V4641 Sgr spends approximately 85 % of X-ray quiescence in the passive state and 15 % in the active .
We analyze passive colors and spectroscopy of V4641 Sgr and show that they are consistent with a reddened B9III star ( with E ( \bv ) = 0.37 \pm 0.19 ) with little or no contribution from the accretion disk .
We use X-ray observations with an updated ephemeris to place an upper limit on the duration of an X-ray eclipse of < 8.3 \arcdeg in phase ( \sim 1.6 hours ) .
High resolution spectroscopy yields a greatly improved measurement of the rotational velocity of the companion star of V _ { rot } \sin i = 100.9 \pm 0.8 km s ^ { -1 } .
We fit ellipsoidal models to the passive state data and find an inclination angle of i = 72.3 \pm 4.1 \arcdeg , a mass ratio of Q = 2.2 \pm 0.2 , and component masses for the system of M _ { BH } = 6.4 \pm 0.6 M _ { \sun } and M _ { 2 } = 2.9 \pm 0.4 M _ { \sun } .
Using these values we calculate an updated distance to V4641 Sgr of 6.2 \pm 0.7 kpc .