TWG Color Manger
You want that your user can choose the colors of the website? You want to create a style sheet that you user can use to modify the colors of you software.
Then the TWG Color Manager is the perfect template for you.
The TWG Color Manager let you select a color from a color palette, convert colors from dezimal to hex and use this color on a layout template on the same page. If the user is done with clicking his color layout he can create a stylesheet and use this for your software.
This script is extracted from TinyWebGallery where the users can select the colors of their layout and generate a style sheet they can use with TWG.