In reference to Ubuntu 18.10 (Cosmic Cuttlefish). Using change login screen purple background 18.10 answer I was able to change screen color for login screen, but the first screen that appears, the cryptsetup pass phrase screen, remained the same purple. I find this color shockingly disturbing, and would very much like to replace it with black or text mode screen.
:While editing appropriate lines in /usr/share/plymouth/themes/ubuntu-logo/ubuntu-logo.script to;
Window.SetBackgroundTopColor (0.0, 0.00, 0.0); # Nice colour on top of the screen fading to
Window.SetBackgroundBottomColor (0.0, 0.00, 0.0); # an equally nice colour on the bottom
does change the pass phrase screen eventually, the purple color still loads for about 3 seconds, then it turns black; like something else is loading color first. It also pops up for a second before desktop background loads.
