Get GRUB Customize:
-------------------------------
sudo add-apt-repository ppa:danielrichter2007/grub-customizer

sudo apt-get install grub-customizer


From:
https://elementaryos.stackexchange.com/questions/3945/changing-grub-background-colour-in-freya

Origonal Creation date in Vivaldi: 1 April 2019 @ 15:42