changing system terminal colours?
Solution 1:
You might find installing grub-customizer to be useful.
sudo add-apt-repository ppa:danielrichter2007/grub-customizer
sudo apt-get update
sudo apt-get install grub-customizer
Also it may interest you to take a look at this question.
Solution 2:
Open a terminal, right click anywhere, and select "Profiles --> Profile Preferences." From here, use the Colors and Background tabs.