it is possible to get the shunt wires turned the wrong way if you (or someone) has disconnected the shunt from the heat-sink and depending on the serial number of your truck, it may even have 2 shunts (one for regen on a heat-sink with only 1 stud diode, and the "main" one mounted to a heat-sink with 2 diodes and a connection to the battery negative power cable, I would expect your question to be about the "main" one)
how do -you- _know_ that the battery is not connected backwards?
are you asking which colored wire should be the one closer to the heat-sink on the "main" current sensor shunt?
the yellow should be the one closest to the heat-sink.

have you had the motor or chopper panel or contactors out lately?