What colour should my book cover be?

Big Bad Book Blog has some advice.

When choosing a color scheme, you and your designer must consider the target audience of your book, the mood you want to evoke, and the symbols that best connect to your book’s content. Then capitalize on the power of color to send your audience cues about how perfect this book is for them.

A few examples of covers that "show how color, paired with compatible symbolism, serve as emotional triggers and help support a book’s primary message" are also provided. Check it out.

The post also points to the web site of Grantastic Designs - an American graphic design outfit - which talks about the psychology of colour in the context of designing web sites and printed materials, but is just as relevant in designing book covers.

Psychology of color: projecting a professional image with color

Color selection is a very important element in your web image because colors have an effect on your visitors before they begin to read the content of your web site. Thus, it is very important for you to consider your target audience, the psychology of color, and the corporate image you wish to project BEFORE you construct your web site.

When color is used correctly, it can add impact and clarity to your message and highlight important points. When color is used incorrectly, it can compromise your message and confuse your target audience.

Color can work for your web site and printed materials in various ways:

1. Color emphasizes, highlights, and leads the eye to important points or links.
2. Color identifies recurring themes (i.e. titles and subtitles are usually the same colors).
3. Conversely, color can differentiate, such as different colors in pie charts and bar graphs.
4. Color symbolizes and triggers emotions and associations.

The interpretation of a color depends on culture, profession, and personal preference. In general, the colors red, orange, and yellow are "exciting" colors and the colors purple, blue, and green are "calming" colors.

Albatross Books had introduced colour coding on book covers in 1932, but colour coding on book covers came to prominence with the launch of Penguin Books in England in 1935. Penguin covers had three  horizontal bands, with the upper and lower bands coloured and the middle one in white. The colours used were orange and white for general fiction, blue and white for biographies, green and white for crime fiction and a pink colour for the travel series.