The following trick only works if it is convenient disconnect the end of the wire.
I strip the jacket off landlubber Romex wire, and cut it down to one inch bits, which make a perfect surface to write on with a Sharpie. Then, I use that no-shrink tubing to label my wire. It does not look fancy
but, being over 45 years old, I really enjoy being able to write in big, legible letters.
I also use a printing machine that produces neatly printed adhesive labels, but my experience has been that these labels fall off over time (I suppose that, like me, my bilge pump is entitled to crunchy snacks from time to time), and that they can become illegible because of heat/light/chemicals.
Most Electricians will be overjoyed to provide you with bits of unwanted Romex for free.