enable Dark Mode via System Preferences, but if you find yourself frequently toggling Dark Mode on and off, then you might find that jumping in and out of System Preferences becomes a drag. Thankfully, an enterprising Reddit user found a way to create a keyboard shortcut for enabling and disabling Dark Mode.introduced Dark Mode, which replaces the bright colors of the menu bar, Dock, and application's submenus with black. You can
Open Terminal and copy and paste this command:
sudo defaults write /Library/Preferences/.GlobalPreferences.plist _HIEnableThemeSwitchHotKey -bool true
You will need to log out and log back in for the change to take effect.
After logging back in, you can enable and disable Dark Mode with this keyboard shortcut:
For more Yosemite tips, please see CNET How To's guide to Mac OS X 10.10 Yosemite.
(Via Cult of Mac)