In 'Shiva et Dionysos' by  the authoritative Alain Daniélou (Fayard, Paris 1979, also in Astrolabio-Ubaldini, Roma, 1980) we read:

 

"The man has not an unique origin. Four human races of different branches do exist (...). Hesiod writes that the evolution of the man pass through four stages, corresponding to the four races of the Hindus. These four stages are symbolized by four colours: white, red, yellow, and black. Afterwards, the four corresponding human races have a predominating role during the different ages that mankind crosses.  The sage, of the white colour, was the man from the Golden Age, the Krita Yuga. After appeared the warrior, of red colour, during the Rites Age or Silver Age, the Treta Yuga. The yellow man, grower and merchant, is the one from the Age of the Uncertainty, the Age of  Bronze or Dvapara Yuga. Finally there is the black man, craftsman and workman, predominating during the Age of the Conflicts, Iron Age or kali Yuga."