Sometimes you need to transfer custom color swatches from one document to another. This is quite easy to do in illustrator. First, open the target document; that is the document to which you want to copy the swatches. From the Swatches Window, choose the Swatch Libraries menu.
From the Swatch Libraries menu, choose Other Library.
This opens a dialog box which allows you to open swatch files. Swatch files are just Ai files; you can open any Ai document using this dialog box. Open the document which contains the swatches you want to transfer.
This opens a new Swatches window showing swatches from the document we just opened. This is just like what happens when you open one of the built-in swatch libraries. Drag the swatches you want to the Swatches Window of the document, the same way you do for the built-in swatch libraries.