They haven't announced it yet. But you can probably expect White for sure, and probably Black as well. Maybe they will follow suit with DS Lite, and release White, Ice, Navy and Black.
I doubt it. I remember when they showed the colours for the Gamecube when it was first unveiled. Only 2 colours got released at launch I think (purple and black) and it took a LOOOONG time before silver got released and then white.