When to use the RGB atlas and when the CMYK atlas?Due to the fourth colour the CMYK atlas offers many more nuances, but its application only makes sense if the software and hardware being used support the CMYK colour model. 'Software only capable of RGB' and 'Software capable of both RGB and CMYK' (click thumb):Do you know a good image viewer with CMYK support ?In general only software that is customarily used in the preprint stage is CMYK capable. An overwhelming majority of programs only support RGB colours.