There does not appear to be any inconsistency in current Ubuntu releases (unless you count the X being red and the rest of the icon being grey). Is this bug still valid?
** Changed in: ubuntu-themes (Ubuntu) Status: Triaged => Incomplete -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to ubuntu-themes in Ubuntu. https://bugs.launchpad.net/bugs/533403 Title: Mute Icon incoherent in notifications Status in ubuntu-themes package in Ubuntu: Incomplete Bug description: Binary package hint: ubuntu-mono Change the mute icon, use an icon with a loudspeaker with a cross (Notify-osd but in monochrome) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ubuntu-themes/+bug/533403/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp