Color themes allow the use of predefined course colors in courses. The edits made to a theme are immediately visible in all the courses that use the theme. The theme management page shows how many courses the theme is linked to, and also provides access to edit existing themes and add new ones. In this screen, you can choose a setting to force the use of the themes on courses, which means that when creating a course, you are forced to choose one of the available color themes. If the use of the themes is not forced, the creator of the course can choose an existing theme or set the main color and the color of the text manually.
Color themes can also be used in course text blocks. Just select a color for the block when editing the text block in the course.
Tip: Try different color themes for courses and text blocks. In a text block, even just a colored border can make the layout more interesting.