The PDF/A-1 requirements related to color handling may be confusing to users and developers who are not familiar with color management concepts and ICC profiles. This TechNote describes the affected objects in PDF, details the requirements of PDF/A-1 with respect to color handling, and provides recommendations for color strategies in common situations.
Contrary to popular belief, specifying an RGB value for, say, black does not accurately specify any color, but merely instructs a particular device to render the darkest possible color – which will be different on different devices. Similarly, 50% red in RGB may look like a clearly specified color, but it fails to define the red base color to use. Again, the visual results will be different on multiple output devices. These problems can be solved by using device-independent color specifications.
Since PDF/A-1 is targeted at long-time preservation of the document’s visual appearance, device-independent color specification methods are required. PDF/A-1 makes use of several PDF concepts for specifying color without any dependency on actual output devices.