The "Roar" singer showed off her newly-dark hair as she took to the stage for the U.S. TV event, which was perfectly set off by a shiny silver catsuit, red blazer, and a swipe of bright red lipstick.
Hairstylist Jesus Guerrero shared a video clip of Katy's new look on his Instagram page, writing alongside it, "Black hair for #Americanidol finale."
Kim Kardashian was among the stars commenting on Jesus' post, writing, "Stunning!"
However, it appeared the hair was just temporary as fellow judge Lionel Richie was later pictured wearing a black wig, that looked very similar to Katy's glam new look, in a snap posted on Facebook.
She wrote, "@americanidol afterparty thank you @lionelrichie #americanidol," as Lionel struck several glamorous poses.
Chayce Beckham was crowned winner of the competition, beating fellow finalists Grace Kinstler and Willie Spence. His victory came after he performed original song 23 during the semi-finals of the show, and he told reporters after the final that Katy had advised him to save that "ace" for as late in the competition as possible.
"You notice I didn't sing an original for the whole season," he told Parade.com. "I waited until the right time to do it and I think that made a big difference. I played my cards just right. Katy Perry told me something. She said, 'Don't forget to pull the ace that you have up your sleeve.' She told me that because I didn't do enough for my Showstopper performance in Hollywood."
"She said, 'You were supposed to pull the ace and you didn't. Don't do that again.' They gave me another chance, and so I waited and waited and waited for the right time to pull my ace, and I did. So, I think that definitely affected the outcome."