Not in the printing; in the writing.
Colorless writing is boring. In his blog, journalist (The Economist) and teacher Andreas Kluth writes:
Color has to be in support of something. And that something has to be an idea, a thought, a story. The mistake many writers make is to list details. Lists are boring; we use them to go shopping. Details are boring, unless they illuminate some meaning. It does not have to be epic. It can be quirky, amusing, moving, insightful, whatever. But there has to be a there there.
So the trick is to find substance, and then to take away details so that only a few splashes of light and color remain, which then filter out the entire sensual world around the reader and deliver him to that one place that you, the writer, have in mind for him. In terms of thought process, it may be the opposite of what my students were doing, and what I used to do.
I can find no better illustration than Rembrandt. You are drawn deep into this man. If I asked you, you would say that there is so much color in this painting, so much light. Only then would you notice that most of the canvas is dark, that very little of it is … in color. (Click here to see what he’s talking about.)
Thanks, Andreas. That works for non-fiction books, as well as for journalism. You want to take your reader on a journey, but it must be purposeful. I was once on a flight from the east coast to California, and the pilot took us down for a view of the Grand Canyon, because the day was beautiful. The view was fantastic, but I learned later that the pilot was severely reprimanded for departing from the flight plan. Several passengers, it seems, felt they had been taken for a ride they did not ask or pay for. Your readers deserve to get where you promised to take them, too.