What type of light? Light bulb or LED. I am assuming DC control, not DCC.
Light bulbs are not polarity sensitive. LED’s are.
There will be a difference for the install.
Before DCC. 1.5 volt light bulbs were used with six diodes for forward and reverse lighting. The lights came on a lot sooner than old twelve volt bulbs.
http://www.mrollins.com/constant.html
Edit.
You might do it with a diode for twelve volt bubs. Put a single diode in series with one lead for forward light and another for rear light. Proper wiring and the diode will block the current blow when polarity is reversed but never did this. Just a guess.
I used 1.5 volt bulbs and constant lighting many years ago..
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Adding lights to old diecast Mantua 0-4-0. Can I just wire the tender backup light leads backwards to have it come on in reverse?