Tour Plone 5: Enhanced Theming
Plone 5 uses Diazo, the advanced theming engine that makes it easy to install, activate, create, modify, and reuse beautiful themes – entirely through the web.
Diazo maps your site's content to the theme elements you want, through XML rules you create using an intuitive point-and-click builder.
Everything about your theme (CSS, images, JavaScript, mapping rules) is grouped together. Themes can be exported and imported easily. Changes to themes can be made live immediately, and the theming control panel includes what you need to preview your changes, invalidate cache, and compile LESS.