Raiden is the eternal God of Thunder and former protector of Earthrealm. After the second defeat of Shinnok, he ascended to the status of Elder God. Being a god, he possesses many supernatural abilities, such as the ability to teleport, control lightning and fly. As a god, he is used to thinking in terms of eternity rather than normal human lifespans, and as such he has a radically different outlook on life. Although being formless and ethereal, Raiden often takes form on mortal planes. As such, he appears as a fully-grown man wearing predominately white robes and a blue vest, his face usually shadowed by a straw hat. The effect is enhanced by his glowing blue eyes that radiate with electricity and long white hair, befitting of his god-like status. In Mortal Kombat: Deadly Alliance one of his outfits is finished by a flowing blue cape. Lastly, his power is so great that he constantly radiates with lightning energy, electricity constantly dancing and crackling around his being. In Deception and Armageddon, his visage was warped by Onaga's malevolent aura when he sacrifices himself, reforming as a dark warrior dressed in black robes and dark armor, his eyes changed from a soothing blue to a animositive red. His cape was changed to a subdued red and appears tattered at the end. Due to the events of Mortal Kombat (2011), this change was rendered null.Raiden's vs in MKT
Good, although recently, he has been depicted as an angry and vengeful god who, in his game ending, killed Shujinko for endangering Earthrealm (in other words, he's tired of humans putting the world in frequent danger, and he wants Earthrealm to stay safe). Interestingly, his MK ending also humorously depicted him inviting other gods to compete in Mortal Kombat, and it resulted in the destruction of Earth (however, this was before his role as a mentor to the heroes had been established).
It's worth noting that in production art unlockable in the "Krypt" in Mortal Kombat: Deception, the new Raiden design used after the revival of Onaga (black and generally darker in appearance than in previous games), is described as belonging to "Dark Raiden." Additionally, during an encounter with Shujinko in Konquest mode, the new "dark" Raiden offers to train him and warns him that he's "not the Thunder God you once knew."
In MK 2011, Raiden appears in his original form, although his "Dark Raiden" outfit is his alternate costume.