Builder 2.0, Communities new experience, and system pages such as Order Forms use style guides. They determine the colors, and fonts used by default.
NOTE! This guide shows how to manage system wide style guides (from the Account Settings). To manage landing page style guides (from your 2.0 Landing Pages), head to this guide.
The changes in system style guides affect all system pages and community pages. This includes courses, forums, groups, order forms, scheduling links, etc
You can edit your current Style guides under the Marketing tab > Style Guides:
To change your current System Style guide to a different one, click on the button ‘Change’, pick another available Style guide or create a new one, then click on Select.