DVI is only 24-bit color as far as I'm aware. HDMI v1.3 will support higher color depths, assuming that source components and displays both follow suit. Since HD-DVD and Blu-ray weren't developed with that in mind, I don't know how soon we'll see hardware that makes good use of that. The PC world is a bit different, as video card drivers and monitors have supported color depths beyond 24-bit for some time. In the meanwhile, HDMI v1.2a and below is still 24-bit just like DVI - and all of our source components and displays.