Install grub-theme-starfield by entering the following commands in the terminal:
sudo apt update sudo apt install grub-theme-starfield
Description:
GRand Unified Bootloader, version 2 (starfield theme)
This is the default theme for GRUB's graphical menu.
Homepage: http://www.gnu.org/software/grub/
Version: 2.02-2ubuntu8
Section: universe/admin