I've upgraded to Photoshop CS6 and like the new darker background color for the user interface. But Camera Raw still has the old style light color user interface which doesn't match Photoshop. I would like it to be darker too but can't find a way of changing it. Is there a way and if so, how ?
No, there's no way to change it. They apparently weren't able to get to all the various dialogs and menus to make the changes.
A secondary issue is that Camera Raw is a plug-in, and I don't know of any way to get main Photoshop configuration parameter information from a plug-in - though one should think that Adobe could find a way.
Frankly, if one of the main goals of the new release was to spruce up the window dressing, one has to wonder why they chose to release it without actually finishing the work. Apparently the release date is king, and everything else, including finishing the work, takes a second seat.