A Bit of a Dark Joke
If you have a parent in the medical field, then you’ve probably heard some things over the years that now make complete sense to you. For example, blue lips usually indicate something bad has happened.
Unless, of course, you have blue lips because you were just eating blue candy. Even then, it’s still an opportunity for a joke–dark humor included. The first time this person’s partner’s family heard this joke, they were pretty stunned.