A lot of UI guides advise against using primary colors as a background for text. I'm in the process of designing covers for a series of 4 books, and I thought it would be good to have a band across the top of the cover that was differently colored for each book. Should I proceed with this idea or move to softer earth tones instead? (this is a print book as well as an ebook)
Background: The plan is to reserve the top 30% of the cover for this color band. I'm thinking of using green for the first book, then red, blue and yellow (I know, green isn't technically a primary color). The front title and the top paragraph of the back cover blurb will reside inside this color band, so the text can't be hard or painful to read. We're planning on using black text on red and yellow, white text on blue and green.
These are technical books, not novels, so I'm not trying to push an overly artistic design, but thought that the bold, primary-esque color choices would establish a strong association between each book and its color. Over time, readers might even look up to the shelf and grab the "red book" or the "green book" rather than think about the title.
I'm not an expert on background colors, text colors or other design issues so I might have come up with a foolish idea here. If so, please show me the error of my ways.