If you have multiple groups of users on your Moodle site you may want to tailor specific themes to certain users.
This can be achieved by enabling either ‘Allow course themes’ or ‘Allow category themes’. To enable these settings go to Site administration ► Appearance ► Themes ► Theme settings and check either ‘Allow course themes’ or ‘Allow category themes’.
Enabling ‘Allow course themes’ will allow you to select a specific theme to display within a course. To force the theme go into the course and click ‘Edit settings’ within the Course administration block, then in the ‘Appearance’ section in the ‘Force theme’ drop down select the theme of your choice.
Enabling ‘Allow category themes’ will allow you to select a specific theme for the category. To force the theme go into your Courses section, and click ‘Manage courses’. Then in the categories section click the ‘Edit’ icon for the category you wish to force the theme. In the editing settings you can then select the theme form the ‘Force theme’ drop down.
If you choose to use both 'Category' and 'Course' themes please bear in mind that using a course theme will override any other theme, including category themes.