I used a hd6950 for 4 years, default color settings, hooked to a monitor (samsung bx2450) and tv (sharp quattron lc40le810un), both calibrated to perfection (from a personal perspective). After upgrading to a gtx 980, I was quite disappointed to find out how dull the colors were, even on Full rgb. Even after calibrating the colors though the control panel and monitor/tv, I can't seem to get them looking quite as good as they did on my old amd card. On top of this, there's apparent banding on backgrounds and blotchiness. Almost felt like a 600$ downgrade.
I thought it was just me, perhaps my eyes were deceiving me or I got a faulty gpu, but after a bit of research it seems to be a common complaint with nvidia cards. The difference might be very subtle to some and escape others, but if you place an example from both amd and nvidia side by side it becomes inescapably apparent. Here's a site I found with a few side by side in game comparisons (290x and titan). http://pokde.net/pokde-blog/nvidia-gtx-titan-vs-amd-r9-290x-image-quality-comparison/#prettyPhoto
So what exactly makes amd cards better in this department? Does it use a form of dynamic contrast among other things, higher saturation, improved blacks, etc, by default to improve the color scheme?