As Mac does it, Ubuntu could provide a small widget at the bottom of the Properties window (main tab, where there is plenty of room) where the user can quickly click one of several colors to set the folder to that color. Easy to access, and no words or explanation necessary.

Rationale
I thought this idea had already been suggested, but I guess I'm wrong. I've read some suggestions for Ubuntu to organize its user files as Mac does in its Finder, so the nitty-gritty of the operating system is hidden from view. I don't think Ubuntu needs to do that, but I do think it would be a great idea to color code folders.

Ubuntu's current folder-marking system isn't great.
GNOME's Emblems are a neat idea but don't provide much functionality to basic users. For one thing, it takes too long to access the Emblems tab for someone to micromanage many folders by choosing an emblem for each folder.
For another, in Ubuntu's current default theme, most emblems are of the same color and merely have different designs. If you're quickly browsing through many folders, this won't allow you to identify the right folder as fast as a folder of a different color would.