CxF stands for “Color Exchange Format”, an open XML format for the exchange of colour information, which is increasingly being implemented by software manufacturers to attach information on the colour behaviour and overprinting behaviour of spot colours to PDF files, for example. This information can then be read and interpreted by proofing software to optimize colour reproduction in a proof.
Ideally, the CxF/X file then describes the spectral measurements of the spot colours (on paper white and, to determine transparency, on black) and is used for colour communication and data exchange between customer, designer, agency and printer.
For the freieFarbe e.V. CIELAB HLC Colour Atlas the achieved spectral values of all colour fields are published as CxF3-file which can be used e.g. by colour manufacturers and software like InkFormulation from X-Rite.
Further information can be found here: