This is an interesting topic but I think we need to be very clear about which version of the falcon we're talking about, and which had red light and which did not.
ANH
- The original 5 ft. falcon for ANH did not have any lights
- The Original Set piece in ANH did not have any lights.
ESB
- 32" Falcon - built with lights - white headlights in the front. one per mandible in the center . the other black areas are weathering smudges.
- 5 foot falcon - added lights mandibles. These were also white. the holes on the top and bottom (4 each) depicted above are part of the model part used for the 32" falcon. They are not actual holes.
- Set piece - lights added all over this... white spots all around the bottom, and red marker lights on the landing gear and the front of the mandibles.
- The Bespin take off shot - that was an addition during the Special edition makeover, as an FX. the model did not have red lights when filmed.
ROTJ
- Setpiece - remained largely unchanged form ESB. although minor changes were present due to the set being torn down and reconstructed between movies. However IIRC the Falcon set piece does not show up in the movie as the sandstorm scenes were cut, and the rebel hangar is a matte painting.
- The 5 foot and 32" models were almost identical to ESB. The only differences in the models being minor repairs and paint work to fix issues resulting from the models going into and out of storage.
The long and short is that the models only have had white lights on the mandibles.
The Set pieces had red and white lights added.
Clearly the Falcon is supposed to have red lights on the mandibles as well as white. due to the FX shot that added the red lights and the set piece having them.
The result is you can add them or not and be correct in your build

as long as the "headlights" are white, and the marker lights are red.
Make sense ??? :rolleyes
Jedi Dade