Looks like the next step would be to test with an older NVIDIA driver version from the Ubuntu repository, and maybe with the slightly newer version 390.77 from the NVIDIA website also.
** Changed in: xfce4 (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to nvidia-graphics-drivers-390 in Ubuntu. https://bugs.launchpad.net/bugs/1767711 Title: Nvidia+XFCE: Totem window is see-through during playback, colours washed out Status in nvidia-graphics-drivers-390 package in Ubuntu: New Status in totem package in Ubuntu: New Status in xfce4 package in Ubuntu: Invalid Bug description: Since the upgrade to Ubuntu 18.04, the Totem player will show everything behind it during playback, and the colours of the video are washed-out. https://i.imgur.com/0AwJMmf.jpg I did not find 'tranparency' nor 'opacity' setting in the program preferences, and the colour adjudgement settings are pinned to +/-0. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: totem 3.26.0-0ubuntu6 ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17 Uname: Linux 4.15.0-20-generic x86_64 NonfreeKernelModules: nvidia_modeset nvidia ApportVersion: 2.20.9-0ubuntu7 Architecture: amd64 CurrentDesktop: XFCE Date: Sat Apr 28 14:56:29 2018 InstallationDate: Installed on 2016-06-05 (692 days ago) InstallationMedia: Xubuntu 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.1) SourcePackage: totem UpgradeStatus: Upgraded to bionic on 2018-04-27 (1 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-390/+bug/1767711/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp