Ever since version 220.127.116.11 (x64) on Windows 10, I noticed that most icon sets didn’t render properly. For example the automatically chosen set “colibre” was unusable due to nebulous icons. The two sets “elementary” & “tango” were working fairly good, only a few icons displayed murkiness.
The icon style setting is found in “Options >> LibreOffice >> View >> User Interface”.
Apparently a similar problem is a “scaling issue on 4K monitors in Windows 10”, more info (here).
I first tried to disable OpenGL, since I read that it was a valid fix for melanized icons (here). However that problem was actually specific for “icons rendered as black squares”. Luckily I recently found a simple solution to my issue, by poking at things.
The solution turned out to be deleting the icon cache, stored in your user’s roaming folder.
On my computer found in this location “C:\Users\feather\AppData\Roaming\LibreOffice\4\cache\colibre”.
You can type %appdata% in the address field of windows explorer, which takes you to “…\Roaming”.
I hope this will be of some help, and either way Have a wonderful day!