Perhaps the top and bottom lamp having different colors serves a purpose not too different from using green and red to designate port and starboard. The nautical idea is to identify facing for a ship that's in front of you. If you see red and green lights, you know the ship is heading towards you ... especially if green is on the left and red is on the right. You're then supposed to pass green-to-green. That is, your starboard side to his starboard side. In Trek, by adding un-colored lights under the saucer in the same general position as the colored lights, you now know that a ship in front of you is upside-down if there is a white light directly above the green light. Without them, if you saw a ship with its green lights on the right and its red lights on the left, you might assume the ship is heading the same general directioin you are. But it might be upside-down relative to you and thus heading towards you -- especially since there appears to be no mechanism for obstructing the running lights from behind. [EDIT: This is my speculation for colored on top, white on bottom, not established Trek convention.] So the lights should be arranged to tell everyone, at a glance, your orientation and general heading in an environment that allows ships to move three dimensionally. Unfortunately, the original Enterprise is missing some more lamps that would help this make sense; red and green lamps on the tops of the nacelles, for instance, and the secondary hull in case the saucer has separated and the secondary hull is maneuvering independently. And you're certainly welcome to your take on things! But -- as you say -- "big" isn't the same as "bright", and whenever I see those huge bulbs on the ship, I don't see a design philosophy that says "these domes are big to make them visible", I see two, magnificently out-of-scale incandescent bulbs. The filament must be as thick as rope!