It appears as though the toolbars are pulling colors from the background theme. How would I get that to change? Is this a setting that can be manipulated with Libreoffice settings or is it going back to the gtk theme?
You cannot. I’ve also tried everything. LO does not pick up the Windows high contrast toolbar background (black), and so the toolbar is white on white. LO cannot download the Firefox themes. The advice they provide if you google it is non-applicable or useless.
It’s a very old question, but if anybody stumbles across it…
I had the same problem running LO under Linux Mint. I found that changing the Linux Icon theme solved the problem for me. (Start button, preferences, themes)
I think I had a dark theme active when I installed LO, and it seems to have selected a set of icons that look good against a dark toolbar background. I then changed the Linux theme to a light theme, and could hardly see the LO icons. It seems LO picked up the new background colour for the toolbar, but didn’t change any icons. When I changed back to a dark theme LO reset the toolbar background to a dark colour and I could see all icons.
If you are trying to change the toolbar background color because the icons are not contrasting properly (ex., you’ve set a dark desktop theme, but the LO icons are still black), you can change the icon style (in newer versions of LO) under Tools → Options → LibreOffice → View → Icon Style. [Verified using KDE 5.68.0 on Kubuntu 20.04 with LO 6.4.3.2.]
For more info on icon styles, see this article: https://libreofficehelp.com/change-libreoffice-default-look-and-feel/