What if you want to access custom brush and fill swatches in a different file? It can be done. Illustrator lets you open the Swatch library of one file within a different file.
One useful technique is to have a special Illustrator file just to store fill and stroke swatches. From that file, you can import that set of swatches into any open document and access your full library of custom fills.
Follow these steps to open a swatch or brush library from one file into a different open file:
With a document open, choose Window Brush Libraries or Window Swatch Libraries, depending on whether you want to import brush stroke swatches or fill swatches from another file.
Select the Other Library submenu option.
Double-click the Illustrator (AI) file from which you want to import a swatch library. The new (additional) Swatches or Brushes palette appears in your open document.
You can access brush shapes or swatches directly from the imported Swatches or Brushes palette.