Duplicating swatches can be useful when you want to create a warmer or cooler variation of an existing color. Note that duplicating a spot color will result in an additional spot color printing plate.
Select a swatch, and choose Duplicate Swatch in the Swatches panel menu.
Select a swatch, and click the New Swatch button at
the bottom of the panel.
Drag a swatch to the New Swatch button on the bottom of the panel.