How do you change the default skin of a Liferay theme?

Changing the default skin of a Liferay theme can be effectively accomplished by updating the "liferay-look-and-feel.xml" file. This file contains configurations for look and feel attributes of themes, including the default skin settings. By specifying the desired skin in this XML file, you can control how elements are rendered across the site.

While other options relate to different aspects of theme customization, they do not directly pertain to changing the default skin. For instance, using the Control Panel is a user interface method for changing settings but may not provide the granular control that editing the XML file offers. CSS overrides allow for modifying visual styles at a finer level but do not change the underlying skin that dictates the overall theme structure. Lastly, modifying the theme.json file is often relevant for theme configuration, but it does not specifically handle the default skin aspect as clearly as the liferay-look-and-feel.xml file does.

Thus, updating "liferay-look-and-feel.xml" is the most direct and effective method to change the default skin of a Liferay theme.