Now why you ask....
because they were not painted at the same time as the bodies....you will note that anything body related is painted body color and then the body was lowered onto a lower unit (frame, front fenders, radiator, engine, light bar, lights, etc) without regard to body color.
So as the frame didnt know the body color it would get; the light bar had to be painted black.
If you look at the splash aprons you can readily see that they were pre installed on the frame before the body came down on it.
True...rear fenders were different but fronts were the same in a model year except when fender well(s) were installed.
If you think about how the car was assembled the colors of the components makes sense.
IMHO that is.
Dennis L Oberer
Green Bay WI