Dipping brass cases in "Insta Blue" will turn the bottom of the case black. I like to cover the area above the web.
I use this system, multiple rifles of the same caliber or when using powders that are not very temp insensitive, one for Summer loads, one for Winter loads.
I have notched the base of the rim with a small triangle file, also.
Dying the brass with Insta Blue is very obvious. Somewhere in your reloading notes, it is a good practice to write down just what that means to you. I still have brass that I was shooting on one rifle from the 80's....like a note in the top of the case guard box.