HKSoft :
Maybe too late for the answer? I using LG 27UD68 (IPS 4K 10bit support) and I just bought GTX970 day ago. There is 10bit output option in nVidia control panel. Hope this what you are looking for.
http://imgur.com/UDUu2u0
that doesn't work in windowed applications -ie Photoshop etc
Don't know about windowed apps. But on my LG I get the same thing and have since my 970's and 1080's too. You can visibly see a difference between the 8 and 10 as well. The 8 is blander with colors less vibrant. On 10 its almost like looking at a really amazing painting. I'm researching this since someone called me out on another thread about no gtx support and only quadros.
Bottom line is most info is out of date. I remember when this option showed up in CP. It was around 3-6 months after the 970's came out. Suddenly on some my 1080p displays I now even had a 12bit option. When I got this LG it was no problem switching to and holding 10bit. You can see the differences!
I tried the NEC demo some talk about. Its pdf specifically states its for multisync PA displays. Don't have one, didn't work. Not counting it as a valid check.
Nvidia really just needs to get its act together put out some credible current info. I know there's many different ways of displaying colors but to say there's no 10bit on the GTX's and only the Quadro's and no WIn10 support isn't completely accurate. Maybe one format on one and not the other but that doesn't mean none at all.
I also believe there could be a lot of missing driver support in programs to properly access what different cards offer. It's easy to believe they're targeting whatever is in the Quadro's and completely missing other options.
and that's the point, nasty nVidia