The after latest avast one free update the system tray icon turns grey when avast is fully loaded mouse over shows system is protected and all the sheilds are turned on if I disable them the icon turns to orange again with the normal warning highlight but the icon is grey in normal status.
This really should be in the Avast One for Windows sub forum - https://forum.avast.com/index.php?board=126.0.
I don’t use Avast One, so I can’t check.
I just wonder are you running Avast in Silent Mode, don’t know if that would have a colour change in the tray icon.