Currently there is some kind of tentative support for themes in LibreOffice which doesn't work to well. IMO, most people want to have a "light theme" and a "dark theme". Just like in Windows. Most people probably don't care about other, more esoteric color themes. The problem is that currently there is no good support for a dark theme which colors all panels and widgets. Ideally this dark theme should color everything. People requested dark theme in Windows for a long time. I'm sure in LibreOffice it would also be welcome.
*** This bug has been marked as a duplicate of bug 118320 ***