Each plugin can be provided with its own /styles.css script to customise that plugin's look and feel. Over and above that, Moodle provides a flexible plugin-based theming framework--check out the Moodle directory at https://docs.moodle.org/dev/Themes. A new Moodle theme is possibly one of the more complicated plugin types you might need to develop. Go to Eclipse and navigate the PHP Explorer to the theme folder:
The trick to developing a new Moodle theme is to take a pre-existing theme and modify it to your requirements. Take a look in the Moodle plugins directory (https://moodle.org/plugins/browse.php?list=category&id=3) for third-party themes.
Let's take a look at the general structure of a Moodle theme plugin. In Eclipse, open the theme/canvas folder:
In the previous screenshot, you will see two folders that have been expanded: layout and style...