I think this is more about the quality of the surface itself. It needs to be perfectly smooth to allow for laminar airflow. If it gets painted over with all those little anomalies, dents and several layers of paint you lose those advantages. So better take a factory provided cover that is stock colored but supersmooth surfaced. And keep it clean.
Excellent! It's going to look great! I think there are lots of other ways to make up for the lost efficiency, (pretty small I would say) but brand identity takes priority here and I wonder if other airlines will follow suit.