Dave composed on 2017-08-03 10:23 (UTC-0400):
Video now looks like 8 color mode....
On 30th July, I did an update/upgrade on Ubuntu-16.04. I should have known better when it wanted to update X-server and Grub on the same shot....Computer boots OK stops at TDM login screen..normal. but the graphics in the background picture look awful....
Start by showing us Xorg.0.log from /var/log/ or ~/.local/share/xorg/. You can use pastebinit from a vtty login if unable reach https://pastebin.ubuntu.com/ or https://pastebin.com/ in a browser to upload it.
Other clues might be found with 'dmesg | grep fail'. If you see any that look like could be related post them here if few, or pastebin if many.
Given it happens in XFCE too, a query among Ubuntu email or https://askubuntu.com/ users might provide more expedient help.