As far as I know, black is a standard colour and white has been a standard colour too since 2003. As for any other colours I don't think they repeat them, however some colours like the Seafoam from S/S 2004 and the Turquoise from F/W 2004 look a like...
I don't know if you've heard of this site, but it's fantastic, if you're a Balenciaga fan
atelier.naff 