Black and Gray basically means tattoos done with use of degrees of black to gray shading. There is usually no application of color at all, although depending on the design a small amount of color can be added to enhance areas of the design.
This type of tattoo is particularly suited to darker skin tone, which does not accept color well, and also to those who are regular sun-worshippers or solarium addicts.
Time tends to soften the tones of the piece and give it a realistic depth quality.