Fuel Filler Neck.... Paint or not?

[ironman24]

Hi guys, 
  My gas cap wont stay on so im replacing the Filler Neck.  My question is....  Should this part be Painted to match the car or is it left metal color like it comes.  The one that is on my car is black to match the car.  But im just wondering how they should be and what some other guys did... paint or not? 
thanks,
Chalrie

[x77-69z28]

bare metal. the gas tank went in after the car was painted.

[ironman24]

Thanks!