I think I know what is wants, yes there is different route signs built into these cars the only thing is you can't change them in the normal manner using change destination command.
If I rember right it is part of the car number. try this
Check the car number on the side of the car
Use the ? to call up the car properties
Now check what the car number is in the properties, if I have remembered right you will find it has a extra digit at the start or end, this digit can be from 0 -9 there is 10 different destinations built into these cars,
You can also change the car number as long as you keep within the correct group and add this extra digit back in the right place for the destination.
The Low V cars are even more intresting when you change them the lamps on the roof at the ends of the cars also change between Red, Yellow, Green, White and none.
Hope this helps
Tom