the cells themselves are not color coded
they are marked with a + sign for positive
and a - sign for negative
there are other ways to identify the pos/neg terminal of a battery also if they are not physically marked

if a company were to mark a positive lead in black and a negative lead in red then they would be leaving themselves open for some serious lawsuits as they would be going against international convention

there are some things in wiring that are just not reversed

like the green wire in house wiring is always the earth ground, red and black are always positive and negative - respectively