Colourways can be duplicated and deleted from a document very easily. How you do it is a personal preference. 

Duplicating colourways in the Layers Palette

1. Use the arrows at the top of the Layers Palette, or the Colourway Chooser (opened by clicking on the number at the top of the Layers Palette) to select the colourway you want to duplicate.
2. Press the + button to the right of the arrow buttons. The selected colourway will be duplicated, and the visible number in the Layers Palette will change to indicate the number of the newly added colourway.

Deleting colourways in the Layers Palette

1. Select the colourway you want to delete using one of the methods in Step 1 above.
2. Press the - button to the right of the arrow buttons. The selected colourway will be deleted.

Duplicating colourways in the Colourway Chooser

1. Open the Colourway Chooser by clicking on the number at the top of the Layers Palette and select the colourway you want to duplicate.
2. Hover your cursor over the colourway you want to duplicate and press ⌘J (command and J) on your keyboard. The highlighted colourway will be duplicated. 

Deleting colourways in the Colourway Chooser

1. Open the Colourway Chooser by clicking on the number at the top of the Layers Palette and select the colourway you want to delete.
2. Hover your cursor over the colourway you want to delete and press ⌘⌫ (command and backspace) on your keyboard. The highlighted colourway will be deleted. 

Duplicating colourways in the Colourway Browser

1. Open the Colourway Browser by clicking on the highlighted icon at the top of the Layers Palette and select the colourway you want to duplicate.
   
   

   
   

2. Select the colourway you want to delete and press the + button at the top of the browser. The highlighted colourway will be duplicated. 
   
   

Deleting colourways in the Colourway Browser

1. Open the Colourway Browser and select the colourway you want to delete.
2. Press the - button at the top of the browser. The highlighted colourway will be deleted.