Tachometer installation trouble

My Lancer CC 1996 didn't come with an orignal rpm gauge in the dash so i bought a new one and i have no idea how to install it. I know that there is four wires, black, red, white and green. I have a fair idea where to put most of them exept the green one! Can anyone Help me?? please

My Lancer CC 1996 didn't come with an orignal rpm gauge in the dash so i bought a new one and i have no idea how to install it. I know that there is four wires, black, red, white and green. I have a fair idea where to put most of them exept the green one! Can anyone Help me?? please

BLACK = ground

RED = Ignition power

WHITE = MINUS on the Coil

GREEN = bulb (light) PLUS