sass-cmyk

https://github.com/sandersk/sass-cmyk

Need to preprocess CMYK colors with Sass? The sass-cmyk plugin lets you construct CMYK color objects with cmyk(), adds support for performing math operations (+, *, /) on CMYK colors, and provides functions for mixing and scaling color components. sass-cmyk outputs CMYK color values using cmyk() function syntax supported by AntennaHouse and PrinceXML PDF formatters, making it a great fit for doing print typesetting with CSS.