I have a Top banana Charger.

If I were to install neon lights on the underside of the car waht color would go with Yellow?

 

Since its a Top Banana.....only yellow and white neons would look good. Now, were you to start adding additional colors to your car....say like a yellow and blue graphics.....or yellow and green graphics....then you could look at other colors.....

It's all a matter of opinion in the end....but I tend to view neons as something you try to color match to the car.....be it a color on the car's accessories (rims, convertible top, graphics, interior) or the color of the car itself.