ColorSet is a macOS utility and framework allowing developers to manage custom interface colors with ease

ColorSet is both a macOS application and a macOS Swift framework, ColorSetKit.

The application lets you create files containing colors and variants, just as an Asset Catalog File, while the framework allows you, in your application, to retrieve colors from the .colorset file using names, just like the macOS 10.13 SDK

Additional information about the app and “how-to” are available on GitHub