Can you help me?

[Messchird]

I don't know this techinque's name.
While I was doodling, I did this techinque by accident.
It's this techinque where you do the background as black and white and grey and you do the person in colour. Do you have a term for this?

Here is a example of mine.

What do you reckon?

[A D]

Dunno the name, but you saw alot of it in Sin City the movie.