Remember that feature from Gnome Panel that made the Nautilus' window background red when using it as root?
Some months ago, when Panel was replaced by Shell I wrote about bringing that feature back, since it's really useful if you are using multiple file manager windows and one of them as root. It prevents you to accidentally do something as root that would potentially do some harm to your system.
That idea (http://community.linuxmint.com/idea/view/2546) was originally marked as rejected, I think because the Mint team was not enough involved with the Nautilus team to do something about that, and later marked as considered again.
Since things changed a bit since then, and the Mint team is coding its own file manager, Nemo, and is cooperating with the Mate team with their Caja, I think its time to bring this idea up again: red background when using Nemo/Caja as root.