You can create a new banner and choose the color you want and also customize the text color. It is also possible to position the banner on the right or left. You have the possibility to save the banner and use it for later.

Banner on the right or left

Change color and safe Banner for later

Please see the Icons command line tool wiki page.

Right click on the selected icon and select Make Icon Set. If you do not have write permissions in the folder where the app is located, this will not work.