barely
the point is a wider data path(bus) allows the computer to take bigger bites of data at a time thus making it faster, but the catch is there has to be apps to take advantage of it, at this stage there arent very many yet........its been out for years yet microsoft just started supporting it
apple even to this day with the 64 bit PPC architecture still does not have a 100% 64 bit OS, while most of it is, some of it is still 32 bit
anyway, it wouldnt change the color depth to begin with, thats a video card issue and how the OS deals with it