Screen selection to save power

So the instinct is great but here's a question for the techy types. The watch can have a positive display (black font white background) and a negative display (white font on black background). Now when the watch is off the background is white which suggests to me that the positive display is more efficient as the only pixels being activated are the black ones. Correct me if I'm wrong. If this is true would it be significant because I much prefer the negative display. TIA.