When I use a standard Windows aero theme in Windows 8, the VS2012 lets me to choose between light and dark themes, but I created myself a convenient high contrast theme in W
Here's the register change that changes the high contrast skin into the dark skin in Visual Studio 2015. By applying this file you can use the dark skin when Windows runs in High Contrast.
USE AT OWN RISK!!!
Export the reg values for the High contrast and Dark skin from HKEY_CURRENT_USER\Software\Microsoft\VisualStudio\14.0_Config\Themes\ (You can see which one it is at the value from the name field)
Change the GUID in the Dark Skin export to the GUID from the High Contrast skin export. (Use "Replace All" to do this) (The GUID looks something like this: {a5c004b4-2d4b-494e-bf01-45fc492522c7})
Addition: Copy the values from the Workflow Designer part of the High Contrast skin export and paste it in the Dark skin export (this layout is better than the Dark skin layout for this designer)
Save the changed Dark skin export and execute it while VS2015 is not running.