File with an .ACB extension contains a headline with title, version and number of colours of a set of non-standard colours – their names, codes, RGB and CMYK components, saturation, shade and brightness. It is the so-called colour book file, utilised by the Adobe Photoshop graphic edition software, and also InDesign and Illustrator.

ACB files are helpful during defining a colour set to be used in a specific context, for instance compliant with certain printout standards, or displayed on a specific type of monitors. Several sets are added to the program in the installation folder. They are also adjusted to the ANPA, DIC, FOCOLTONE, HKS, PANTONE, TOYO and TRUMATCH colour catalogues.