Last few years, I use small squares (about 4" across x 3" heighth) cut from a punctured white vinyl fender float. I don't think there is anything as to what color. I notch out a hole towards the left corner & tie a small length of nylon cord to it. I attach this to the end of a line (one on each side. I use a magic marker (permanent black) to write Name & Address on one side. On the other side I mark the date & update by marking over & writing new one below the previous one. Once full, I may replace the tag. Sometimes I can scrub off the older dates, sometimes not so lucky. But if I bring it home, I can usually get it off scrubbing with a bleach cleaner. From time to time, you may need to brighten up the tag (as gunk builds up- use a small nylon brush).
You could use plastic pieces from an old jug, but they get brittle & break up. No tag means illegal line, regardless of what happened & can be removed by a Game Warden.
Previously I used to use small squares of sheet metal plates (from printing), but etching them with a pencil marker can take a little more effort. Plus they get gunked up fairly fast & need to be scrubbed often to stay legible. Plus you have to fold the edges to keep from getting cut or cutting the line folding over on one corner as to attaching.
A small bottle should work too. I just happen to have or use old pieces of a fender float, as I use the fender floats for my Planter trotlines (for deep water) out on the main lake. From time to time, boats may puncture one. Since I utilize 2 to 3 on each side, one for anchor line, one for drop line, and one for higher level (in case lake rises), if one gets ruptured, I still have access to my line. In this case, the float or even a jug can have the tag information & be legal. As to a jugline, the information & date can be on the jug (or float) instead of a tag. Actually that makes for it being easier to identify a legal line for a Game Warden.
If you use a tag or small bottle, then you need to follow the rules on where to place it. If you mark visible jugs or floats, that bypasses the placement rules. Since I set my lines under the surface (those in shallow water), I use tags to identify them.
Hope that helps some.