去https://www.gnome-look.org/下载grub主题
解压，进入到解压后的文件中使用sudo ./install.sh
安装完后将/usr/share/grub/themes/下的主题复制到/boot/grub/themes/
sudo cp -r /usr/share/grub/themes/seek /boot/grub/themes/
修改kali-themes.cfg
sudo vim /etc/default/grub.d/kali-themes.cfg
sudo update-grub
重启