How To Reinstall Trisquel GNU/Linux Default Graphical Boot Up Splash Screen

Hello,

I'm using Trisquel GNU/Linux 6.0 amd64. I recently installed Debian along side it and naturally Trisquel's Grub was overwritten by Debian's Grub. I wanted to use Trisquel's Grub so I decided to reinstall it using the command below:

sudo grub-install /dev/sda

Trisquel's Grub is now back, but Trisquel's lovely graphical boot up splash screen has disappeared :-(

My question is, how do I go about reinstalling the splash screen?

Thanks in advance,

Steve