# Edit Grub bootmenu
sudo grub-mkconfig
sudo nano /etc/default/grub

# Add os-prober for dual boot+
# Remove "#" in Grub infront of os-prober
sudo os-prober

# Save updated grub config to grub
sudo grub-mkconfig -o /boot/grub/grub.cfg

# Menu colours
[Source: https://www.gnu.org/software/grub/manual/grub/html_node/Theme-file-format.html]