Using color will enhance the visual appeal of a web site and will set a mood or feeling for the audience. Proper usage of color can also contribute to the visual hierarchy of a Web page which aids the user in understanding what they are supposed to do on that page.
The Color section of the University ID page describes the standard colors that should be considered when building an official Cal Poly Web page.
Be sure your web site meets accessibility requirements for color contrast and luminosity. See the 508 In-Depth Color - Checkpoint (c) section.