Created attachment 124618 [details] Screenshot of the toolbars using the Breeze theme on Ubuntu 16.04 I had LibreOffice 5.0+ in Ubuntu 14.04 LTS, and the Breeze theme icons were perfectly visible. Recently, on April 21, 2016, I updated my system to use Ubuntu 16.04 LTS. Ubuntu 16.04 seems to use a dark theme for its toolbars, meaning that the dark icons are nearly invisible on the dark toolbar and making normal use extremely difficult.
You have the “libreoffice-gtk3” package installed. That package is experimental. Remove it and LibreOffice will display as it used to be. (If you somehow got the package automatically on upgrading, that’s a downstream — distro — bug.) There’s another bug report here, requesting that these icons be dynamically recolored (useful for e.g. high-contrast mode), but for now, either remove the package I indicated, change to another theme (Radiance, for example), or use another icon theme. See https://pad.lv/1562513