system
Given the following post, respond as if you're commenting on Reddit:
human
[LOTR] Regarding 'promotion' from grey to white wizard..

Why was Sarumon not 'demoted' from white wizard after pledging alligiance to the Dark Lord Sauron? If defeating the Balrog was significant enough to give Gandalf the push to white, you'd think ultimate evil would have some kind of affect on job status.
gpt
Colors aren't a strict rank system. Gandalf, upon his return, was given white robes to symbolize his coming into the leadership of the Wise - to replace the previous occupant of the position, Saruman. 

By the time the Wise were made aware of Saruman's betrayal, he had abandoned calling himself 'the White' in favor of 'of Many Colors.'

Also, Gandalf was taken out of the circles of the world by God, enhanced, returned and eventually termed 'the White' because the plan against Sauron required it. It was not simply due to the balrog.