Auto companies (particularly the big 3) are always on the lookout for ways to cut costs (and cut corners). I don't doubt that it was once silver and it's now black. They probably thought that no one would notice, so they could save a nickel.

I want to know, why did DC decide to paint all the base cars black? Does black happen to be the cheapest color to paint a car, because its a common color on the market and can be bought in volume (thus cheaper), impossible to mismatch (there is only one shade of black), or what? You figure, the finish has to be superb with black, because it's pure contrast and reflection. The tiniest bit of orange peel would show, so finish quality had to remain superb (and it is).