I'm very late into act 3 and she has completely stopped talking and is stuck with one dialog response if you manually speak to her (cannot even remove from my party) since coming in to act 3, so I would believe the note from the other poster that it is a bug. She hasn't had nearly as much content as any of the other companions by a long shot.

Red lights don't allow you to see as well in dark/poor visibility conditions that are needed for driving. You're moving 30 to 60 mph likely on the road vs walking speed while hiking and that reaction time visibility is much more important. The intensity of red light that would be needed would make the benefit non-existent (as they'd be just as obnoxiously eye-destroying as the super brights and blue lights).

Some states in the US allow "amber" colored lights for headlights/brights though, and I think they're way less obnoxious and still allow for high levels of visibility.