At first let's try Color Matching. Just select color collection and enter your RGB. You can find best matching colors here. Color Harmonies are also very interesting. Enjoy! :tu:
Take a photo that you plan to use on the site, or one with colors that suggest the site's theme (i.e. bright, pastel, dark, serious, earthtones, fun ...).
Open the image in photoshop (or other advanced graphics program).
Filter-> Pixelate -> Mosaic (in Corel/Jasc it's Effect->Distortion effects -> Pixelate ... at least in the older versions)
This breaks the picture into blocks of solid colors.
Use the eyedropper tool to sample and record color codes from 5 - 10 of the largest areas.
Don't have a Pixelate filter handy? You can also convert the image to a .gif and reduce the number of colors to get a similar effect (do NOT allow "dithering"), but the other way's a little nicer.
If you're using a photo, this is THE way to match page colors to the photo !