Color is a form of communication. It is important that you can clearly state the concept that you are trying to convey in your designs and select the colors that support that concept. First you need to understand color and its meaning for your users.
Over time each color has taken on a certain significance and meaning. The colors you use in your designs will psychologically influence
how your user feels about your site and product/service.
Various colors can have a different meaning depending upon the culture. When creating websites for an international market you need to research in-depth the colors you are going to use to make sure that the response from the user is the one you expect.
Colors can also be in or out depending upon the trends of a particular year. If you look back over the past decades at graphic design, fashion and interior design you will see that certain colors come to represent certain time-periods