You have also decided who you will aim you site at. So the theme of your graphic design is going to establish how you will be seen and dealt with. It is going to codify all of these efforts. It MUST be consistent and match your concept of what your site is about. The colour scheme and font selection will enhance your theme.
Colours convey a important emotional response in humans.
They are the first impression and will help determine if your site is seeking to be warm, and friendly, exciting, exotic, intriguing, inviting or serious. They set the stage that the other elements will act upon. There is an underlying meaning in your selection that transcends the actual words written on the page. Look at the ad section of a newspaper or magazine. Notice how the graphic presentation of the written word is aimed at a target demographic audience.