In art and design certain colors are often used to help manipulate the way one feels, evoking a certain mood or creating a message or sharp response in the viewer. Whether its to create a calming effect, express happiness, or hint at violence, color is a powerful and effective tool to subliminally convey these messages or feelings.
Color choice is often an extremely important attribute we have to consider when creating the design of an album. Not only will the colors we use directly influence the way a viewer interprets the artwork, but ultimately, the music too.
Here is a great article that expresses how the hidden meaning of color can be used as a powerful tool in art: http://www.finearttips.com/2009/08/use-the-hidden-meaning-of-color-in-your-art/