Within themes it is possible to set variables. These variables go into a styles.xml file. You can find documentation about creating a styles.xml file on the “Advanced Customization with Type, Spacing & Images” page on concrete5.org.
After you created the contents of your styles.xml file, you are able to paste that into a field called “Styles.xml”. This is located under the “Styles” tab, directly under the main “Professionals” tab.