The file extension acb is used by the image editing software Adobe Photoshop for so-called Color Swatches files. In these color palettes are stored. These consist of a collection of color codes, names and color space specifications such as RGB, LAB or CMYK.
ACO Color palette files are used, for example, in image editing to save color palettes for reuse or to match a particular color standard. Depending on the intended use of the image (screen, print, etc.), certain color catalogs are better suited than others.
You can access the color palettes in Photoshop by clicking on the small arrow in the Swatches window. Photoshop already offers a number of different libraries included, including ANPA, FOCOLTONE, PANTONE and TRUMATCH.
With such ACO color files, colors of an image can also be saved as a color palette. In addition, there are thematically sorted ACO files on the Internet for download. To be able to use your own ACO file, you have to save it under 'Preferences / Swatches' in the Photoshop program folder.