The increasingly popular, and increasingly subtle and detailed, style comes from prison culture. “Black and gray used to be referred to as joint-style or prison-style, because of its roots in penal institutions, where inmates made homemade machines from ballpoint pens, guitar strings, needles, and parts from old boom boxes. The machines had one needle. No color ink was available in lock up, so the ink was black. But if you watered it down, it turned gray.”