This is because https://hg.mozilla.org/mozilla-central/rev/ccbe695b5f40#l6.12 made the toolbarbutton.bookmark-item rules more specific by adding :not(#bookmarks-menu-button), which means it now beats the .subviewbutton rule and so the toolbar hover style is applying instead of the panel one.

Comment on attachment 8390452 [details] [diff] [review] Australis bookmark subview hover color is wrong when in main menu panel, Review of attachment 8390452 [details] [diff] [review]: ----------------------------------------------------------------- I like it! Thanks for fixing this.

remote: https://hg.mozilla.org/integration/fx-team/rev/6213d1669c1a

Comment on attachment 8390452 [details] [diff] [review] Australis bookmark subview hover color is wrong when in main menu panel, [Approval Request Comment] Bug caused by (feature/regressing bug #): Australis / bug 909349 User impact if declined: bookmark items in the menu have the wrong hover color Testing completed (on m-c, etc.): on m-c Risk to taking this patch (and alternatives if risky): very low String or IDL/UUID changes made by this patch: none