Gmail Dark Theme
It's easy to change the color scheme in Gmail so that your inbox listing has light text on a dark background. However, the individual emails you open or write will still be black on white.
To change the theme in Gmail, navigate to settings by hitting the gear icon in the upper right area of the screen. Then select Themes, scroll down and pick the onewith the black background.
YouTube Dark Theme
When you go to the movie theater, they turn the lights off to help you see the movie better, so why would you want a white background surrounding your video player? To turn the lights down in YouTube, click on your picture, select Dark Theme and toggle the switch to on.
Visual Studio Dark Color Theme
If you're writing an app for Windows, chances are that you're using Microsoft Visual Studio. The development environment makes it easy to go into dark mode. Just navigate to Tools->Options->General and select Dark from the Color Theme pulldown.
You can also choose custom background and foreground colors by navigating to Tools->Options->Fonts and Colors.
Notepad++ Dark Themes
My favorite development tool, Notepad++ is a text editor on steroids. This must-have piece of freeware lets you view files side-by-side, do advanced search/replaces and get all kinds of visual cues to help with your coding.
By default, Notepad++ has light text on a dark background, but the software comes with a ton of preinstalled themes, including many different dark ones. Navigate to Settings->Style Configurator and then choose a theme from the list. I recommend Bespin or Blackboard.
Reddit Night Mode
When you're sitting in a dark room, combing through the posts on Reddit, you don't necessarily want a bright white screen staring back at you. Fortunately, the social network makes it very easy to change to a dark theme. Just click on your username (or a down arrow if the screen is too narrow) in the upper right corner of the screen and then select Night Mode.