I had never seen any PC more than 32 bit color quality let me know about vista as i am not aware of thatin 32 and 64 bit vista
32 and 64 bit Vista refers to the 32 bit and 64 bit CPUs not GPUs (video card). I have heard of newer video cards going beyond 32 bits of color, but monitors and TVs cannot take advantage of it, and would we even see it? Also check this out if you want: http://en.wikipedia.org/wiki/Color_depth
Actually the top color depth is 24bit. 32bit is just a marketing term as they are counting non-standard settings in the depth. This offers 16,777,216 options of different colors. It is extremely unlikely for this to change in the near future. This is so many colors that adding more will not help much. As others have said, when talking about 32 and 64bit computers it is referring to the CPU architecture. The more bits you have on a processor the more functions it can do at the same time. The processor speeds are in a binary format of counting: 2bit, 4bit, 8, 16, 32, 64, 128. The days of 8bit were back in the days of DOS, 16bit was at the end of that same time and start of Windows 95. 32bit has been from Windows 98 until now.
I think new LCD tvs have deeper color, so called x.v. color or deep color. Here's a link to a press release of it and a quote: "Deep color: HDMI will support 30-bit, 36-bit and 48-bit color depths for stunning rendering of over one billion colors in unprecedented detail." "http://www.hdmi.org/press/pr/pr_20060103.aspx" Not sure what this means for PCs, but deeper color (>32-bits) is currently being taken advantage of by select hi definition TVs and sources.