Hi Tim. Hope your day has been good to you.
I purchased an updated Mac Mini (i5) last week and noticed that display output from it was unusual (both on a monitor and an LCD TV - both Samsung). Grey on a white background did not appear on the screen, fonts were grainy and the screen was overly bright and under contrasted. This issue occurred both from the built in HDMI port and a Moshi Thunderbolt to HDMI adapter. A 2011 Macbook Air I own displayed perfectly on the same monitor and TV using the same settings.
I took the item to a Genius bar in an Apple store and after performing some troubleshooting and diagnostics they agreed that the output was odd and that it must be a hardware fault and so promptly swapped my Mini for a new one.
The second Mini has exactly the same problem. Interestingly, when booted from Windows / Boot Camp the output to my display is just fine. Further, this is not a new problem, having been picked up on Apple Support Communities in July 2012 on 2012 Macbook Airs using an external screen (https://discussions.apple.com/thread/4080525?start=0&tstart=0). OS X updates and an Air firmware update subsequent to July 2012 have not corrected the problem.
This problem would have only sporadically been picked up by Air users because Air users would sporadically use external monitors. But Mini users must use an external monitor and many of these are HDMI only (as is mine) so it seems that we are in possession of a product that is somewhat unfinished and somewhat unusable.
Hope this is of interest to you.
I'm sure he'll get back to me soon.