In addition to the “Klassic Skins” DLC, NetherRealm Studios also have downloadable characters coming to Mortal Kombat. The first of these is Skarlet, a red female ninja:
Interestingly, Skarlet has a history similar to Ermac, the red male ninja variant. While both Ermac and Scarlet — as she was dubbed at the time — were thought to be new characters in Mortal Kombat II, they were actually the result of colour glitches involving Scorpion and Kitana.
Scarlet glitch image sourced from the Mortal Kombat Wiki.