I used the latest version 7 of LibreOffice. When the doc went back to the creator - using Office 365 - they called to say that they could not select and remove the highlighting and had to delete and retype the coloured words.
IIRC, because this doesn't really make sense, libreoffice just has highlighting which allows arbitrary colors, but it can be confusing because it may by necessity become background shading when you export as a word file.
Unfortunately, the UI for background shading is absolutely terrible in Word (there are different types of border/shading settings and you have to open the menu but then select the correct type to even see the current settings that are being applied) so people who don't know about it will be unlikely to figure out where it is or how to change it.
Unless one can supplant the current ".docx" is standard across industry I don't see how your expect others to use a different format.
Personally, I wish odf were the default along with libreoffice.