With car wiring, they aren't necessarily using the colours to define function, they could be using them to define number codes.
There is a colour code used in electronics where numbers are assigned to each colour.
So a Red wire with a green trace could be Wire 25, rather than a +ve wire. A green wire with a black trace, Wire 50, rather than -ve. In my car, Wire 50 was the panel lighting and it did not
like being connected to ground.