Comment # 11 on bug 1231806 from Tristan Miller

I'm seeing this in Wayland, and also experiencing a similar icon problem in
X11, where the main Thunderbird window has the correct icon in the window title
bar and taskbar, but Thunderbird's individual dialogs (message compose, event
reminder, etc.) have their own black-and-white icons:
https://bugzilla.mozilla.org/show_bug.cgi?id=1930699  Not sure if the two
issues are related or not.