This style is pretty self-explanatory; it’s meant to look like a realistic photo of the subject matter on your skin.
Black and gray realism uses gradual variations of black and gray to recreate a photo. Color realism requires extensive knowledge of color theory and the ability to expertly blend colors in order to reproduce your reference picture.
A high level of skill is needed for both types of realism, and the subject matter can be anything from a lovely still life to a portrait of your favorite person or pet.