No they didnt make Impala SS' in white. Someone might have painted it but more likely it is a Caprice with Impala rims, since the back end of an Impala is no different than a Caprice, only the front fascia has a black grill that is the only difference. So it is most likely a white caprice with perhaps some Impala rims.
Impala's came in Black, Grey-Green, DARK Red. I am talking only about '94-'96 Impala's. I don't want anyone accusing me of misinformation when they post some blue '64 Impala or something!