It’s due to a process called triboluminescence. Triboluminescence is what occurs when a Wint-O-Green Life Saver candy is crushed in the dark, letting off a little glowing spark. Triboluminescence basically means light caused by friction, and is the cause for lots of things we see.
It’s to blame for the blue light given off when lightning strikes, for example. In the case of Life Savers, when a high enough difference between negative and positive charges is formed, electrons jump across fractures in the candy, reacting with nitrogen, producing a glow.
A similar thing happens with band-aid wrappers and postal envelopes. When separating certain sticky surfaces, a similar reaction to that in the Life Savers occurs, causing a light blue flash.