haha I didnt think that but your right.
Wait I just had a thought if he dided while the dunmer where chimer why does he have dark skin?
Ghost
It's unclear as to why he has dark skin. We are told the seven Ash Vampires actually survived the Battle of Red Mountain and were scattered and absorbed into different houses or went into hiding. They'd have theoretically been fully mortal when Azura placed her curse on the Chimer, and thus became Dunmer.
The Tribunal themselves were changed as well, but had the powers of gods. Almalexia chose to fully revert to her previous form. Sotha Sil remained a Dunmer and even comforted the other Dunmer about their new appearance. Vivec, forever the contradiction, could not choose and split his color down the middle.
Dagoth Ur himself by most accounts was actually dead while all this was happening. To what extent his original physical body was damaged or even obliterated during his battle with Nerevar and the Tribunal, I don't know. For whatever reason he became Dunmer shaded, dark purple-blue. He may have been affected by Azura's curse or he may have chosen his form diplomatically, to appeal to the Dunmer and help them accept him as their Leader once his plans came to fruition.