and to be truthful I can't see how it would work, or why it would be useful.
Obviously you can't mean Windows and Windows\System32 files, because Windows will update those as and when needed, and attempting to track all of those would be impossible.
You mention client. What do you mean by that?
I found software to color code folders, but really need to be able to color code individuals files (e.g., red, green, blue, etc). For example, red would indicate that the file needs to be updated, so I would know to open it. Green would mean that the file is properly updated, so no need to open it to view.
With hundreds of files, I need to color code because I can't remember each client month after month.