With Design Libraries you can reuse assets, colors and typography across your sites, and share them with your teammates.
To start, open Design Libraries from the Tools bar. Create a new library based on the current site theme or My Designs.
Add colors themes and typography to a library from the Theme Manager, or save design assets directly from a page.
Set up a Team Management account to collaborate and share your design libraries with teammates
For more info go to Design Libraries Article.