What kinds of problems are faced when designing documents that the use of color is often a solution to?

What kinds of problems are faced when actually using color in documents?

I'm trying to provide guidance for the next major version of a mature piece of document design and typesetting software. We have a good idea of where much of the project needs to be in this next version, but color support needs to be re-worked to solve real-world problems in the industry.

Since the color portion of the software is something of a wireframe at this point (more like a rectangle drawn with a worn crayon), I would like to learn more about how color is used in this domain. I've thought about it and have done some internet research for most of the night, but I haven't come up with more than three uses:

To draw special attention to various parts of the page

To allow for quick navigation either on the page or across pages

To implement anti-photocopy measures

These are all a little contrived from my personal, very limited experiences, and some don't prompt answers to the core question I'm trying to ask myself:

What kinds of problems are faced when designing documents that the use of color is often a solution to?

What kinds of problems are faced when actually using color in documents?

I likely don't even know what I don't know in this domain, so external references to textbooks/essays/articles are also welcome.