as to the reference Will mentioned, he's talking about the Kerr plans made for the Polar Lights model.
Sorry Anystar, wasn't talking about the plans

What I meant by looking at the model when it was new, I meant The Motion Picture. They did a movie with it when it was new

So what color would those deflector grids have? from the Christies pictures it is clear they painted them black, can see it clearly by looking at the close ups from the sec.hull, and some of the saucer.
But when the ship was new, looking at TMP and TWOK, I think they were bright, bright as in on of the primary colors used, which could be the darkest one used for the aztecs.
So you both can be right with the color.