Installation

git clone https://github.com/rhino-linux/grub.git rhino-grub
sudo mkdir -p /usr/share/grub/themes/rhino
sudo cp -r rhino-grub/* /usr/share/grub/themes/rhino

Then, add this line to /etc/default/grub:

GRUB_THEME=/usr/share/grub/themes/rhino/theme.txt

And finally run sudo update-grub.