Hover background of toolbar bookmark items and buttons

I have created a standard hover background which, using various stanzas, applies to everything except the toolbar bookmark items and buttons. The following code doesn't have the desired effect on bookmarks. What will? The browser toolbox only shows the main window so I have improvised.

toolbarbutton.bookmark-item(hover) { background-color: #6495ed !important; }

I can't think what to use for toolbar buttons such as UBlock Origin.