How to Use Greasemonkey to Customize Facebook Colors

Open your Mozilla Firefox browser and visit addons.mozilla.org. Type "greasemonkey" into the search bar.

Click the "Add to Firefox" button and finish the onscreen prompts to install the Greasemonkey add-on.

Restart your Firefox browser.

Log onto userscripts.org and search for "auto-colorizer" in the search bar. Select the one titled "Auto-Colorizer: Colors Facebook." Click "Install" to install this plugin.

Log into your Facebook account to view the changes Greasemonkey has made to your page. The colors are based on your profile picture. To change the look of your page, simply change your profile picture.

Source.