A dark UI theme that adjusts to most Syntax themes.
There is a matching Syntax theme, but most other Syntax themes work fine as well.
This theme is installed by default with Atom and can be activated by going to the Settings > Themes section and selecting "One Dark" from the UI Themes drop-down menu.
Why do the colors change when I switch Syntax themes. This UI theme uses the same background color as the choosen Syntax theme. In case that Syntax theme has a light background color, it only uses its hue, but otherwise stays dark. This lets you use dark-light combos.