The term Black tattoo can have a verity of different meaning so it important to understand the two basic schools of thought that are derived from this understanding.

First, a black tattoo can mean black light inking which is a very unique type of “glow in the dark” coloring ink which allows a tattoo to glow under a black light, or UV light, normally black light inking is done over a standard ink tattoo to allow features to shine under this special type of lighting, however, you can choose to have a black light or UV light tattoo without any type of standard ink and your tattoo will only appear visible under UV light. 

Second, a black tattoo can be referred to as your standard black and gray or traditional color style which is the tattoo industry standard and most common type of tattoo color seen.