I dont like much on that car at all.
As far as neons, it can be done right. On your silver car, I doubt it.
If it was a white car with white neons it might look tight, BUT!!!! BUT!!!! BUT!!!! you cant show the bulbs. Just not neat in my opinion. Very anti-neat actually.
I like white. Honestly some BMW's look awesome with lights underneath, jsut for show, but dont be "that guy" who drivers with them on. Obey the law.
A black car, with white underneath might also be hot. Red with red maybe. Most other colors just dotn work with their own color. Maybe a nice blue with blue. Like I said, thats about the only colors that it might look nice with. All this once again assumigng your bulbs are hidden.