Master Caution indicates either of the following:
Engine 1 or 2 failed, APU failed, Engine 1 or 2 on fire, Low fuel level ( less than 800 lbs )
The other working lights are the Battery indication (lights up if battery is off) and L and R Generators, both are on the low-right annunciator.
Other warnings are only used during lights test, but aren't really operational.