Spoiler: Vorlons Probably not. They both use the purple encounter suit design, and the Vorlons themselves aren't quite as golden as Kosh, nor are they as pale as Ulkesh. Not that that's iron-clad proof or anything. The color they glow could be as much an act of will as the rest of their appearance, and as Sheridan once pointed out, there's nothing stopping Vorlons from switching suits, and for all he knew, the Vorlons had been sending someone different every time "Kosh" visited home and came back. That doesn't seem as likely, considering how varied the Vorlons who were definitely different acted, like Kosh, Ulkesh, and the Vorlon from the beginning of War Without End, who was either a third Vorlon or Ulkesh with a cold so his voice and chest-lights were different.