Dealing with colors

Monochromatic
A monochromatic color scheme is often considered for sites where content is of extreme importance, or when the opinions presented are of a moderate nature. It can give a site a clean and classic look, but also provides excellent opportunities to let full color photographs dominate. Monochromatic schemes are often appropriate for serious political and business sites such as those of some banks where instilling customer confidence in their experience. They are also highly suited to fashion sites where the understated monochromatic scheme supports the branding, but nevertheless allows the photographical elements to provide a focus.

source: http://www.glasshaus.com/samplechapters/1159/default.asp