Before the crash(the glitch at the start of the game that caused him to malfunction on stage) :
[before the crash, GlamRock Freddy was corrupted by Vanny's virus and would kill off any child that comes in after hours but would pretend to help them]

After the crash(during the game) :
[after the crash, the virus that was coded into GlamRock Freddy's software was deleted and would act according to how he's supposed to.] + [he also originally had yellow eyes  so the workers found it weird that he had blue eyes when he had the virus]