ProofBuddy was designed from the ground up to be customizable so that your proofing site will match your primary website.
Your first step is reading about theme files.
Customization
Sub Pages
Classes
A set of data classes gives you a great deal of potential to customize ProofBuddy exactly how you want it.
Theme Browser
The theme browser allows for one-click installation of new themes.
Theme Files
Theme files are generally simple HTML files, although they may contain PHP code, that you can customize to match your proofing site to your primary website.