The wrap on a battery is there for more than just easy identification; it keeps the battery from shorting out inside your mod. Under all the plastic, a battery is just a metal tube. If that metal is exposed, and touches the metal from your device, it will short. When a battery shorts, it can heat up and it you’re quick you may escape with only minor burns. If you don’t notice it and it continues to heat, it can go into thermal runaway. Thermal runaway is when the heat from the battery causes a chemical reaction that produces more heat that continues the chemical reaction ad nauseam.
It is possible to re-wrap them, so don’t fret if it happens to a newer battery. There are many good resources online that show you how to re-wrap them. If you notice some chips on your old batteries, it might just be time to retire them.
Stay safe! Make sure your batteries aren’t exposed, a naked battery can be dangerous.