If you were to look at an entire file cabinet full of identical narcotics envelopes and realized that you had accidentally filed a currency envelope the exact same size in with them, how long do you think it would take to find it? Answer: about one minute if you use color! Use white envelopes for money, and gray envelopes for narcotics (or any other color but manila), and you will never accidentally misfile one with the other again. 

Another use of color is to take a hint from the very noticeable Bio Hazard sticker. Get a pack of large labels in a very bright color, and stick one on every piece of homicide evidence, regardless whether it' s a gun box, currency envelope or general evidence. Don't ever risk disposing of evidence without realizing it' s from a homicide!

The next paragraph is from a police agency Daily Bulletin. Check out their use of color: 

As a reminder to all staff, when you are booking items into the Property Section, please use the proper color of item tags. If you have EVIDENCE, please use the BROWN item tags. This is the color for the current year and it changes each year. If you have FOUND PROPERTY, please use the ORANGE item tags. If you have PROPERTY FOR SAFEKEEPING, please use the WHITE items tags. If you have PROPERTY FOR DESTRUCTION, please use the BLUE item tags. You don't have to memorize this system, just look at them, as they are printed with the property type that they are to be used for. This system is very helpful to the Property Room staff in maintaining an accurate inventory.