If you're hellbent on using it... All of these are GENERAL statements, it would behoove you to check the manufacturers' website. As these may not apply to the device you have.

Red - Power, usually
Black - Ground
Yellow - Illum, usually
Green - Tachometer signal

1998 Eclipse RS-T - Totaled 4/23/09 -
1998 Eclipse GST - Stroked 2.3l, HX40 fed: Build in progress
2010 Subaru Outback Limited

I hate hipsters.