dolphin_oracle, as best as my limited knowledge works on this, I think the problem happens before lightdm. It seems to me that it might be at plymouth [edit: specifically, plymouth handover], but then I find it harder to understand. There is limited info on the Net at that point. In fact, seeking k...
under sysV, the /etc/init.d/libvirtd init script is what you want to edit. just use any text editor. sysV does not use the systemd service files anyway.
the main kicker, is you can't use systemctl commands under sysV.
likely changing the window manager theme will do the trick. there are thick border variants, and I think the default_hpdi one is pretty good too, and picks up color scheme from whatever main gtk theme in use. Its the one I go with.