As I recall, none of the Favicon Picker extension had any features for changing Bookmark Folders. But then again it's been 4 or 5 years since any of the three FP extensions worked in Firefox. I gave up when the first version died, never wasted my time with 'Picker2 and 'Picker3. You really don't need to "know" CSS to be able to work with "user" code, all you need is the code that someone else posted in a Mozilla support forum. Or a UserStyle to be added to Stylish. https://addons.mozilla.org/en-US/firefox/addon/stylish/ https://userstyles.org/styles/browse?search_terms=bookmark+folder Here's a couple that I found on the first page of a search at UserStyles.org - https://userstyles.org/styles/9091/bookmarks-toolbar-blue-folders-red-bookmarks https://userstyles.org/styles/46947/bookmarks-toolbar-fx4-blue-folders-red-bookmarks

Favicon released a new version that works with the latest FireFox (31.2.0) You can download/install it from here: https://sites.google.com/site/sonthakit/bookmarkfaviconchanger