I found color coding, subject headings, surnames etc., too confusing for filing ORIGINAL materials. I finally settled on numbering each ORIGINAL consecutively from 1 to infinity. I keep a MSWord index in my Genealogy folder on my computer with a separate page for each surname.
Every time I get a new source I add it to the index and file it in a plastic archival page protector and put it in the binder. The B1 first entry below is for binder number 1, page number 2. As I get more binders they will be B2, B3 etc. You can use any codes you are comfortable with. I can easily search this document using the Find command. Larger items like maps, books etc can be filed in a closet, file cabinet or safe, just use a location coed that makes sense and isn't duplicated. Once I have entered all information from the new source it is filed for safekeeping and I use copies for my working/research binder as needed. Simple and clean.