Can GRUB font size be customised?
GRUB/Tips and tricks

# Choose a font, in this example I chose DejaVuSansMono.ttf
# Convert the font in a format GRUB understands:
sudo grub-mkfont -s 36 -o /boot/grub/fonts/DejaVuSansMono.pf2 /usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf 

# Edit the /etc/default/grub file adding a line:
GRUB_FONT=/boot/grub/fonts/DejaVuSansMono.pf2

# Update GRUB configuration with:
sudo update-grub2