Black and Gray Tattoos are very common in the tattoo industry
The reason why black and gray tattoo's are the most common is because you can do any style of tattoo in black and gray. This type style of tattoo involves shading to help make your tattoo pop out.
This type of style has a wide range of design's you can choose from which make's black and gray tattoo's so diverse.
you can come at a black and grey tattoo in so many way's, for an example you can do very light grey shading or come at the tattoo with heavy black, your mind is the limit when it come's to what you can do with a black and grey tattoo. There are techniques you can find the one that call out to you.
I you want you can also start you tattoo off with just black and grey and later in life if you want you can actually come back into the tattoo shop and add color into your tattoo and give it a twist no one will see coming.