cant remember which is ground wire,help.

[kuatto]

well After taking my old canopy apart and reinstalling the mh light in the knew canopy,I foregot which is the ground wire
The power cord comming from the socket that plugs into the wall has 3 wires,green,black and white.The back of the mh socket has 2 posts,silver and a gold colored(which i think is the positive,if memory serves correctly).which of the 3 colored wires is the ground?

Jim