In the process of revamping a client's filing system recently, I recommended using matching colored interior and exterior file folders to help identify different parts of her world: family, bills, home etc. (This system is described in detail by Erin Elizabeth Wells in this video.)
While color-coding a filing system is a great long-term organizational tool, it can also be expensive. This particular client already had a vast quantity of manila interior file folders, so she opted to use those instead of buying more. Then she purchased exterior hanging folders in five colors and some small colored stickers.
The major advantage to the color-coded system is that you don’t have to think so hard when it is time to put the file away- you know a yellow interior file will go in a yellow exterior folder.
To achieve the same effect without purchasing new interior folders, we used stickers on the file tab of each manila folder that matched the corresponding exterior hanging folder. If we happened to use an exterior folder color that did not have a sticker color to match, we used markers to make a little dot on the manila folder.
The biggest challenge with a filing system is maintaining it. Creating it is the easy part! Taking the extra time to make the system as fool-proof as possible will only save you headaches later.