Define Black Night Meaning

A night of particularly severe drug or alcohol abuse accompanied by suicidal or self-destructive feelings in order to black out and forget about problems with a significant other or a break-up
Popularized by the song of the same name by Time Again.

When somebody is so black that there are completely invisible at night except for their eyes and teeth

Somewhere very dark, when it is hard to see anything

When committing a crime the individual partaking in it would prefer to be dressed in all black, witch makes sense at night seeing it is easier to blend in all black at night however being all blacked out in the daytime is suspicious and ironically draws more attention to person. To combat this a person who commits crimes should where neutral colours during the day, preferably grey to blend in and not seem dodgy however at sunset it would be in your best interest to wear all black. Therefore the phrase "greyed out in the day blacked out at night" came to be.