Normally when you Hide an application in the Dock the icon is hidden and not visible, with this tweak hidden apps will show in the dock with a translucent icon.
Start a new Terminal session (in Finder click Applications > Utilities > Terminal).
To enable this setting, type (or copy and paste) the following command:
defaults write com.apple.Dock showhidden -boolean true
To reset this setting to the default value, type (or copy and paste) the following command:
defaults delete com.apple.Dock showhidden
To activate this tweak immediately, type the following command, or wait until the next reboot:
Close the Terminal session by typing
exit at the prompt.
Disclaimer: Making any changes to your system can cause serious problems that may require you to reinstall your operating system. We cannot guarantee that problems resulting from these modifications can be resolved. Please follow the instructions carefully and use the information provided at your own risk.