Error: symbol 'grub_term_highlight_color' not found.
Entering rescue mode.
grub rescue >
To fix this, the only way I know is to re-install grub2. So, I booted into a live cd and used the boot-repair utilities:
sudo add-apt-repository ppa:yannubuntu/boot-repair && sudo apt-get update
sudo apt-get install -y boot-repair && (boot-repair &)
I just used the Recommended repair option from the above window. The utilities led me through several steps including instructed me to run some commands to remove grub, then re-install it. After the restoring process finished, I restarted and everything back to normal. \m/
For more information about boot-repair, please read this manual page: https://help.ubuntu.com/community/Boot-Repair