Grub Theme

On Kubuntu

Copy the theme into the grub themes folder:

sudo cp -r path_to_theme_dir /boot/grub/themes/folder_name

Open the grub config:

sudo vim /etc/default/grub

Update or add these configurations:

GRUB_TERMINAL="gfxterm"
GRUB_THEME=/boot/grub/themes/folder_name/theme.txt

Apply the changes:

sudo grub-mkconfig -o /boot/grub/grub.cfg