Change background colour on an individual Custom Content box

Each component should have a class on it that includes the name of the component.  For example on this page, the breadcrumb at the top is wrapped with div with a class called "lia-component-common-widget-breadcrumb".  You should be abled to use these classes to specifically style an individual component.  For a custom content area you will likely need to add a div inside your custom content and style that.  All custom content areas have the same class on them "lia-component-common-widget-custom-content".