Pretty much most Mac systems show a red indicator on the System Preferences in the Dock when there is some type of System update available. That is fine for most people, but not for me. I run a Developer Beta of the latest macOS on an external hard drive. So, my main system on my iMac recognizes that I am a Developer and continually indicates updates for the latest Beta in the System Preferences icon in my Dock. This is very annoying to me, I don’t want to run a Beta on my main machine. So I found a way to turn off that indicator. Perhaps you don’t want to move to the latest version of the macOS. For whatever reason, you can turn off that indicator by following the instructions in this article. It involves using the Terminal, but it is easy to do or undo.