Grub2 theme
Grub2 theme based in StylishDark
sudo ./install.sh
/boot/grub2/themes/
/etc/default/grub
:GRUB_THEME=/boot/grub2/themes/grub2-solarized-dark/theme.txt
for Fedora grub2-mkconfig -o /boot/grub2/grub.cfg
UEFI
grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg
for Debian update-grub