I am looking to make the wiring updates in my home extremely simple to understand while doing so in a code-approved manner.
I cannot find anything against wrapping a thin band of colored electrical tape around the outer sheathing on NM-B wire such as a small band of red tape around the yellow jacket of the wire below at each junction/fixture to help identify which circuit each wire belongs to.
A colored electrical tape pack is what I was thinking of picking up:
Basically, I was thinking of adding two thin colored bands to identify the main runs of the branch circuits (using up to six colors for each band: black, white, red, blue, green, and yellow). And then I was thinking of adding two more thin bands to identify the branch connections to receptacles off of the main runs. However, I am unsure if labeling the sets of 3 wires (for 12-2) with a couple small bands of electrical tape would be against code (such as wrapping the sheathing with green electrical tape since green is typically used to mark ground wires) or actually make it more confusing. Answers that include best (or typical) practices are very welcome (even if the typical practice is to not mark the wires at all).
EDIT: While I agree with the update to the title to make the question a little more general, I am still interested getting an answer to my proposed solution about using colored electrical tape bands from the perspective of the NEC (2008 or later). I certainly appreciate the answers that suggest labels on the wires, but case in point, my hand writing is terrible and I think color is a lot easier to identify at a glance than trying to read little numbers. The way my home is currently wired with knob and tube inspired the thought because the original wiring truly was in an extremely structured, well-crafted manner and is really a work of art to look at (each hot wire for each branch circuit of the existing knob and tube wiring is a different color that is both easy to understand and follow throughout the house). I plan to create a full set of "blueprints" (in color with color-coded wiring) and keep an updated printed copy of the diagram with the electrical panel so I am still favoring the idea of color-coding the wires if it is NEC-compatible.