Does anyone know if the top section of the trailer tow mirrors is removable so you can change from a white painted section to a black section to match the rest of the mirror?

 

Yes, the top "skull cap" is removable. Pop off the top piece of glass and then remove the 4 nuts that hold the skull cap on.

To get the glass off tilt the mirror all the way to one side, then slide a flat blade screw driver behind were it clips on too. Slowly work it off, be careful not to break the glass while doing it though. It is only held onto the mirror by a few small clips.