Not sure why no one else has chimed in, I know the original grill trim piece has a gray/silver paint towards the inside, probably the light argent, I have NOS sport lamp grill, if I were to paint , it would look like dogshit. Same goes for the honeycomb panel. I read through that link, the painting of the black is referring to black painted on body to hide car color in gaps that are not covered by honeycomb panel, rocker mouldings and headlight surrounds. If u didn't paint these areas the body color would shine like the sun and look bad, I have original paint on my car. The area under the honeycomb looks like it was taped and painted neatly, the areas under rocker mouldings looks brushed on. I have seen guys on the 428cobrajet forum brushed in the headlight buckets. If u do paint your grill, post some pics. If its a show car, u should really get Jeff or ed meters or some other real pro to lead u/us on the correct path my Mustang brotha.