/usr/share/plymouth/themes/ubuntu-gnome-logo/ubuntu-gnome-logo.grub is in plymouth-theme-ubuntu-gnome-logo 16.04.4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | if background_color 45,51,53; then
clear
fi
|