The new Dark Mode in OS X Yosemite, which gives the OS X Menu Bar and Dock a dark background, can be enabled it in System Preferences.
“That method is fine if you just want to pick the default light mode or new dark mode and stick with it, or change it only infrequently, but what if you want to enable dark mode frequently and on the fly?” Jim Tanous asks for TekRevue.
Tanous reports, “Instead of a trip to System Preferences, here’s how to enable and disable dark mode in OS X Yosemite with a quick keyboard shortcut.”
Easy instructions are found in the full article here.