Working on XFCE desktop environment – I wanted to Change Preboot & Login Screen Background (Its a terrible shade of pink).
XFCE unlike Genome has far fewer GUI editing options.
I googled for a solution but could find none. (there are several posts that show how to do that on genome – but none that showed how to do that on the XFCE desktop environment)
The xfdesktop manager allows to set the background color or set image for the desktop but does not allow setting the pre boot or login screen setups.
I finally discovered that you can do this by editing the file
/etc/lightdm/lightdm-gtk-greeter.conf using any file editor like gedit or nano.
sudo gedit /etc/lightdm/lightdm-gtk-greeter.conf
This should open up a file that has cotents like:
# background = Background file to use, either an image path or a color (e.g. #772953)
# theme-name = GTK+ theme to use
# font-name = Font to use
# xft-antialias = Whether to antialias Xft fonts (true or false)
# xft-dpi = Resolution for Xft in dots per inch (e.g. 96)
# xft-hintstyle = What degree of hinting to use (hintnone, hintslight, hintmedium, or hintfull)
# xft-rgba = Type of subpixel antialiasing (none, rgb, bgr, vrgb or vbgr)
# show-language-selector (true or false)
Simply edit the background image or a color code or change over to a different theme to get rid of/ change the Preboot & Login Screen Background in XFCE