You can either use the existing color sample library file or create new one, both ways will work.
With existing color sample library file , select color rectangles and change color and save as a new library file, you can repeat this with different color sets for separate individual sites.
New file can be created with different colors , Go to Library Panel > Create New Folder. Open Page and then insert the contents ( whatever you want to include in your library file such as color rectangles, text frames , image, widgets etc ) , select them all > right click > Add to Library and then select the new folder that you have created.
You can use the created library file for multiple pages, different sites , different layouts such as phone, tablet, just drag the library combination from panel to your page.
If you have question or doubt with this , let me know I will create a short video for you.
and also, if its not regarding the color sample library file but with color swatches that you are referring then please let me know.
Thanks,
Sanjit