More accurately, according to the book "Leftism Revisited" by Erik Kuehnelt-Leddihn, the original Nazi flags were actually made from communist flags that they already had because the Nazi party was formed from elements of the German Communists that already existed at the time.
They simply sewed a swastika over the hammer and sickle of the communist flags they already had.
The red of the Nazi flag symbolized socialism.
White, the white nation
Black swastika, the Aryan race (a subset of whites)