I need to know where the battery light gets it ground from.Thanks

If the 94 is identical to the 95(I have the 95 EXT580EFI AC manual in front of me).......

The battery light wires are RED/BLUE & GREEN/BLACK. They go through the hood harness.

GREEN/BLACK goes only to a 6 prong rubber plug to the DC Regulator.
In this plug, I see a BLACK wire(which is likely where the light gets it's ground), which goes through a 4 prong rubber plug at the Elec Start connector, then to a BLACK wire back to the Negative Battery terminal. For reference, this 4 prong connector also has RED, RED/WHITE, and RED/BLACK wires

RED/BLUE goes to several places. Here are some but not all.

CDI unit(4 prong plastic plug at CDI)
safety/throttle lever switch(3 prong rubber plug)
pin 116 of small ECU connector
pin 9 of large ECU connector

Also, there is a single pin rubber plug RED/BLUE wire near the handlebar. Check this too.