At the bottom of the color popover, you can store gradient or image fill presets for quick access and reuse within your document or as part of a library. Previously, solid Color Presets would also appear here, but these are now Color Variables.
Adding a preset
To add a preset, select your gradient or image fill, choose whether you’d like to add it to your global (all documents) or document (this document only) presets, then click the 
icon.
To rename your preset, make sure you’re viewing your presets in list view 
, Control-click on it and choose Rename. You can also Control-click and choose to move or copy your preset between the global or document locations.
You can drag presets to reorder them, or drag them completely out of the color popover to delete them (or Control-click on them and choose Delete).
Creating Library presets
When you save a document preset and make that document a Library, it’ll appear below the Global and Document items in the presets menu to anyone who’s added the Library.
Any presets that have been updated in a Library you’ve added will show a small dot to indicate when they’ve been updated.