CMYK colours may be specified with or without a fallback RGB colour for use with media that do not support CMYK. When the fallback RGB colour is not provided, it is calculated from the CMYK colour.
cmyk(<C>, <M>, <Y>, <K>) : CMYK colour with Cyan, Magenta, Yellow, and Black components.
device-cmyk(<C>, <M>, <Y>, <K>) : Equivalent defined by GCPM.
rgb-icc(#CMYK, <C>, <M>, <Y>, <K>) : Equivalent.
rgb-icc(<R>, <G>, <B>, #CMYK, <C>, <M>, <Y>, <K>) : CMYK colour with fallback RGB colour.