/lib/plymouth/themes/kubuntu-logo/kubuntu-logo.grub is in plymouth-theme-kubuntu-logo 1:14.04ubuntu15.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | #set_background_image "images/tile.png";
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
if background_color 0,0,0; then
clear
fi
|