During the 22nd century, dermal art was popular on Denobula. Phlox's parents urged him to learn the art while he was growing up. He used his skills to create faux prison markings on Degra's arm. (ENT: "Stratagem")
In the prequel comic Star Trek: Countdown, it was explained that it was a tradition on Romulus that when a loved one died, those who suffered a loss would paint their grief upon their skin. In time the paint would fade, and with it the period of mourning. Nero and his crew, however, burned their tattoos deep so that they would never fade.