It seems that many greek and roman statues were not white, they were painted, and there are still traces of the original pigment in the marble.
The Vatican Museum put on an exhibition making copies of the statues and painting them based on the pigments that were found.
Though it is quite clear that the painting was not done with quite the consummate skill that the sculpting was.
http://listverse.com/miscellaneous/top-10-color-classical-reproductions/#comment-22911
