Change the folder icon on a Mac by using the 'Terminal' command 'defaults write com.apple.finder FXPreferredViewStyle list' to change the icon style, then restarting the Finder to see the new folder icon on the Mac desktop.

Change the default folder icon on a Mac by going to the 'System Preferences' pane, clicking on 'General', and selecting a new icon from the 'Show this icon as' dropdown menu, then clicking 'Save' to apply the changes and see the new folder icon on the Mac desktop.

Create a custom folder icon on a Mac by right-clicking on the folder, selecting 'Get Info', clicking on the 'Icon' tab, and dragging a new icon from the desktop or a folder to the 'Replace' box, then clicking 'Apply' and 'OK' to apply the changes and see the new folder icon on the Mac desktop.