There are many systems to describe and illustrate colours that are used in many walks of life.

To make some absolutely basic decisions about colour choices, we found this article by Chris Jackson to be very useful when advising clients:-

You know what you want to say, and you know exactly how you want to lay it out. Great, you’re about half way home. Copy and layout are the first part of presenting your information, but maybe not the most important part. Before your audience begins to read and react to your information they see it in color.

Color creates audience responses by stimulating emotions and communicating on levels other than reason and intellect. It can excite, impress, entertain and persuade, but color can also create instant negative associations. It’s a good idea to be aware of how the majority of people respond to color and use this information in your choice of colors. Use the guidelines in the chart below to help you choose the colors that are most appropriate for the message you want to get across.

Color Chart (suggested meanings)
The chart below represents several meaning for color. Each color may represent another emotion to you. Use your best judgment when dealing with color and make sure to get feedback on the colors you use.

When choosing colors for your design, remember a few rules for mixing colors. The human eye cannot focus on red and blue at the same time. Trying to read red type on a blue background or vice versa causes extreme eye fatigue. Your audience will not be receptive to your message if it hurts them to read it. Never, ever use blue type on a red background and even worse, is red type on a blue background.

Most colors go well together with members of the same "family". Warm colors of type, such as red, brown, orange and yellow look better together in combination warm colored backgrounds; cool colored type like blue, green, gray and white with cool colored backgrounds. Using color families generally makes for a more appealing presentation, especially for large amounts of information.

Contrast is fun and can be used effectively to accent information and draw attention to items. In general, keep the contrast low. Too much contrast makes your work difficult to digest. For type, keep the contrast reasonable no matter what colors you’re working with. If your background has a value of, say 20%, and the type has a value of 80%, it presents a subtle look that's easy on the eyes and is graphically appealing. Avoid the extremes.

Courtesy of Chris Jackson