Even older aircraft with the wing tip nav lights of the old school design, the lens and cover are designed to keep the light shining forward and outboard at a 110 degree arc, never aft.
Even the light bulb itself is designed to shine forward and outboard.
If the aircraft is in front of you, you would see the white tail nav light. I never said that in the original question. Only green and red are visible.
If the aerobatic pilot is showing you a planform view of his aircraft, you would see the white tail nav light. Again, in my original question, you only see the red and green nothing else.
Even if holding altitude/heading while inverted isn't easy, it could be done, but your oil and fuel system must be designed for extended duration in that flight attitude.
some more info:
Aerospaceweb.org | Ask Us - Aircraft Lights & Beacons
Maybe this pdf will explain all as it describes the designs and requirements of nav lighting.
http://www.goodrich-lighting.com/catalog/Chapter08_Navigation_Lights/08_0025_Navigation_Lights.pdf?expand=1
I'm just saying that if you see a red light on the left and a green light on the right, you better check your ADI to make sure it isn't you and then watch out 'cause the other guy may be doing rolls or spilled his coffee in his lap and he is coming right at you.
The FAR's explain it all regarding aircraft nav lighting.
Don't get me wrong, this is all good stuff.