Rainbow adds text color, background color and style for console and command line output in Swift. It is born for cross platform software logging in terminals, working in both Apple's platforms and Linux. Thanks to the open source of Swift, developers now could write cross platform programs with the same language. And I believe the command line software would be the next great platform for Swift. Colorful and well organized output always helps us to understand what happens. It is really a necessary utility to create wonderful software.