Themes
Theme support is a work in progress!
In the meantime, you can add CSS (inline or via a link) directly in your presentation. Here is a non exhaustive list of CSS selector you might be interested in tweaking:
.slip-bodyto restyle a slip, eg to add margin, set font size and color….block,.theorem,.lemma,.definition,.example,.corollary,.remark, for admonitions (with special rules when they have the attributetitledefined),Any non-specific elements, such as titles, paragraphs, …