Theme not working on Kali Linux 2025.3 (with solution)

[MarcoConsiglio]

In Kali Linux 2025, install.sh installs the theme files correctly, but the theme isn't displayed.
I followed this tutorial to get the new theme working.

In /etc/default/grub, change the GRUB_THEME variable as follows:

GRUB_THEME="/boot/grub/themes/fallout-grub-theme/theme.txt"

In /etc/default/grub.d/kali-themes.cfg, change the GRUB_THEME variable as follows:

GRUB_THEME="/boot/grub/themes/fallout-grub-theme/theme.txt"

In the same file, add the GRUB_BACKGROUND variable. This will prevent the default theme from being displayed after selecting an operating system to boot.

GRUB_BACKGROUND="/boot/grub/themes/fallout-grub-theme/background.png"

Finally, update the /boot/grub/grub.cfg file with the following command:

sudo grub-mkconfig -o /boot/grub/grub.cfg

Make sure you find the new GRUB_BACKGROUND variable in the newly compiled file with:

sudo cat /boot/grub/grub.cfg | grep 'background'

If everything was done correctly, you will find

if background_image /boot/grub/themes/fallout-grub-theme/background.png; then

Now the theme works correctly! Enjoy!