There's no single car officially designated as the "first black popular car." Popularity is subjective and depends on the timeframe and geographic area. The idea of a car having a specific "black" designation is also problematic as car colors weren't often marketed in racial terms.
Black was and is a popular car color, and many makes and models were available in black throughout automotive history. There's no singular model that stands out as the first to achieve widespread popularity in that specific color.
